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176 Cards in this Set
- Front
- Back
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Cellular (Procaryotic and eukaryotic)
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bacteria, archaea, algae, protozoa, and fungi
No plants/animals |
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Acellular
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viruses, viroids, and prions
often referred to as acellular microbes or infectious particles Can’t cure a virus |
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Strain
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population of cells from a single species descended from a single cell
Genetically identical, 1 1 million . < : branch |
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biotype or biovar
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A strain with a characteristic biochemical pattern (how they use biochemicals such as oxygen, CO2)
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Prokaryotic species
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A population of cells with similar characteristics
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Asexually reproduce** conjugation – pseudo reproduce
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group of strains that share many stable properties and differ from other groups of strains
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Phenotypic
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size, shape
Gram stain special stains culture differences biochemical tests Serology fatty acid profiles |
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3 basic categories of bacteria
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Cocci (round bacteria)
Bacilli (rod-shaped bacteria) Curved and spiral-shaped bacteria |
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Cocci may be seen
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singly,
in pairs (diplococci), chains (streptococci), clusters (staphylococci), packets of 4 (tetrads), or packets of 8 (octads). |
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Bacilli
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Often referred to as rods;
may be short or long, thick or thin, and pointed or with curved or blunt ends. |
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Curved and Spiral-Shaped Bacteria
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Examples of curved bacteria:
Vibrio spp. (flesh eating bacteria) TampaBay Campylobacter spp. Helicobacter spp. Examples of spiral-shaped bacteria: Treponema spp. Borrelia spp. |
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Three Major Categories of Staining Procedures
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Simple stains
Structural staining procedures Differential staining procedures |
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Structural staining procedures
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Capsule stains
Spore stains Flagella stains(type & location, mono,lophotrichous, enpho, etc. |
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Simple stains
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Simple stain stuff to simple see stuff – types of staining, crystal violet, safranin, methylene blue, malachaile green, carbolfusion
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Differential staining procedures
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Gram and acid-fast(microbacteria & norcardia) staining procedures
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Domain Bacteria Staining Procedures
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Bacterial smears must be fixed prior to staining
The fixation process serves to kill organisms, preserve their morphology, and anchors the smear to the slide (superglue) |
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The two most common types of fixation
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Heat-fixation
Methanol-fixation |
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Heat-fixation
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not a standardized technique; excess heat will distort bacterial morphology, water & air dry
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Methanol-fixation
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a standardized technique; the preferred method, not really
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Gram-variable bacteria
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Some bacteria are neither consistently purple nor pink after Gram staining
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Mycobacterium spp. are often identified using
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acid-fast stain
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acid-fast stain
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Carbol fuchsin is the red dye that is driven through the bacterial cell wall
Heat is used to soften the waxes in the cell wall Because mycobacteria are not decolorized by the acid-alcohol mixture, they are said to be acid-fast |
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motility
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If a bacterium is able to “swim”
most often associated with flagella; less often with axial filaments Most spiral-shaped bacteria and about 50% of bacilli are motile; cocci are generally nonmotile demonstrated by stabbing the bacteria into a tube of semisolid medium or by using the hanging-drop technique |
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colony morphology
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includes: size, color, overall shape, elevation, and the appearance of the edge or margin of the colony
includes results of enzymatic activity on various types of media true for cell morphology and staining characteristics, colony morphology is an important “clue” to the identification of bacteria |
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atmospheric requirements
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classified on the basis of their atmospheric requirements,
O2, CO2 |
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With respect to O2, bacterial isolates can be classified as:
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Obligate aerobes
Microaerophilic aerobes Facultative anaerobes Aerotolerant anaerobes Obligate anaerobes |
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Capnophilic organisms
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grow best in the presence of increased concentrations of CO2 (usually 5 to 10%)
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serology
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Combine known antiserum plus unknown bacterium
Slide agglutination test |
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ELISA
Enzyme-linked immunosorbent assay |
Known antibodies
Unknown type of bacterium Antibodies linked to enzyme Enzyme substrate |
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Flow Cytometry
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Uses differences in electrical conductivity between species
Fluorescence of some species Cells selectively stained with antibody plus fluorescent dye |
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Genetics
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DNA base composition
Guanine + cytosine moles% (GC) DNA fingerprinting Electrophoresis of restriction enzyme digests rRNA sequencing Polymerase chain reaction (PCR) |
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There are 3 types of RNA, named for their function
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Messenger RNA (mRNA)
Ribosomal RNA (rRNA) Transfer RNA (tRNA) |
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DNA
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Double helix
Deoxyribose Thymine |
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RNA
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Single strand
Travels Ribose Uracil mRNA tRNA (transfer) rRNA (robsomal) in cytosol/plasm in prok. In ER in euk. cells |
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Purines have
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2 rings
AG is silver. Silver is pure. AG = Purines |
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Pyrimidines have
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1 ring
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For a double-stranded DNA molecule to form...
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the nitrogenous bases on the two separate strands must bond together.
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A always bonds with T via
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2 hydrogen bonds
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G always bonds with C via
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3 hydrogen bonds
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A-T and G-C are known as
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“base pairs”
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The bonding forces of the double-stranded polymer cause it to
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assume the shape of a double alpha-helix, similar to a right-handed spiral staircase
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DNA replication
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When a cell is preparing to divide, all DNA molecules in the chromosomes of the cell must duplicate, thereby ensuring that the same genetic information is passed on to both daughter cells
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DNA replication occurs by...
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separation of the 2 DNA strands and the building of complementary strands by the addition of the correct DNA nucleotides
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DNA polymerase (also known as DNA-dependent DNA polymerase) is ...
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the most important enzyme required for DNA replication
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Replication fork
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connecting point
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DNA polymerase
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unzip your genes
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Leading strand
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- needs to be read
- complementary strand formed (=messenger RNA) – single stranded Process known as transcription |
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Single helix held together by...
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covalent bonds
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Hydrogen bonds b/w nucleotides...
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hold both together
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A gene is a ...
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particular segment of a DNA molecule or chromosome.
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gene product
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A gene contains the blueprint that will enable a cell to make what is known
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It is the sequence of the four nitrogenous bases of DNA (i.e., A, G, C, and T) that ...
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spell out the instructions for a particular gene product.
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Although most genes code for proteins, some code for ...
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rRNA and tRNA
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Some genes code for ...
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more than one gene product
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The Central Dogma explains ...
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the flow of genetic information within a cell (proposed by Francis Crick in 1957).
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transcription
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One gene of a DNA molecule is used to make one molecule of mRNA
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translation
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genetic information in the mRNA is then used to make one protein
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gene expression
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All genes on a chromosome are not being expressed at any given time. It would not be logical for a cell to produce a particular enzyme if it was not needed
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inducible genes
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Genes that are only expressed when the gene products are needed
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constitutive genes
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Genes that are expressed at all times
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transcription
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The process by which the genetic code within the DNA molecule is transcribed to produce an mRNA molecule
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The primary enzyme involved in transcription is...
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RNA polymerase
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In eucaryotes, transcription occurs within the nucleus
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the newly formed mRNA molecules then travel through the pores of the nuclear membrane into the cytoplasm, where they are used to produce proteins
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In procaryotes, transcription occurs in the cytoplasm
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ribosomes attach to the mRNA molecules as they are being transcribed at the DNA – thus both transcription and translation may occur simultaneously
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In eucaryotes, transcription occurs within the nucleus
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the newly formed mRNA molecules then travel through the pores of the nuclear membrane into the cytoplasm, where they are used to produce proteins
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In procaryotes, transcription occurs in the cytoplasm
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ribosomes attach to the mRNA molecules as they are being transcribed at the DNA – thus both transcription and translation may occur simultaneously
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70s ribosome =
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50s +30s
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a codon
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Mrna U-C-C goes into ribosome, move over mrna in order to read it w/ help of trna & read in sections of 3 base pairs, 3 nucleotides
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translation
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The process of translating the message carried by mRNA, whereby particular tRNAs bring amino acids to be bound together in the proper sequence to make a protein
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codons
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The base sequence of the mRNA molecule is read in groups of 3 bases
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anticodon
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The 3-base sequence codon can be read by a complementary 3-base sequence on a tRNA molecule.
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amino acids
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Subunits of proteins
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Genetics
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study of heredity
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genotype
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complete collection of genes
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phenotype
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physical traits (e.g., includes hair and eye color in humans)
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An organism’s phenotype is the manifestation of ...
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that organism’s genotype
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Genes direct ...
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all functions of the cell
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A particular segment of the chromosome constitutes
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a gene
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In order to change phenotype...
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need to change genotype
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Ways to change genes
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mutation
malfunction during replication transcription/translation |
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mutation
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A change in a DNA molecule (genetic alteration) that is transmissible to offspring
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3 categories of mutations
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Beneficial mutations
Harmful mutations (some are lethal mutations) Silent mutations |
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mutagens
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Mutation rate (the rate at which mutations occur) can be increased by exposing cells to physical or chemical agents
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mutant
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The organism containing the mutation
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Ways in which bacteria acquire new genetic information (i.e., acquire new genes):
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Lysogenic Conversion
Transduction Transformation Conjugation |
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plasmid
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An extrachromosomal DNA molecule
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An organism that acquires a plasmid acquires ...
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new genes
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episome
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A plasmid that can either exist by itself or can integrate into the chromosome
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Lysogenic Conversion
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Temperate phages (or lysogenic phages) inject their DNA into a bacterial cell.
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lysogeny
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The phage DNA integrates into the bacterial chromosome, but does not cause the lytic cycle to occur
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prophage
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a phage where all that remains of it is its DNA
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lysogenic cell
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The bacterial cell containing the prophage
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lysogenic conversion
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The bacterial cell exhibits new properties, directed by the viral genes
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Phage uses bacteria as its host b/c...
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it’s a virus
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Temperate phage like galaxy b/c...
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shoots into cell
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Transduction (“to carry across”)
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Also involves bacteriophages
bacterial genetic material is “carried across” from one bacterial cell to another by a bacterial virus; thus, in transduction, bacteria acquire new bacterial genes Note how this differs from lysogenic conversion, wherein bacteria acquire new genetic information in the form of viral genes Only small amounts of genetic material are transferred by transduction |
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Transformation
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A bacterial cell becomes genetically transformed following the uptake of DNA fragments (“naked DNA”) from its environment
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competence
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The ability to absorb naked DNA into the cell
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competent bacteria
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bacteria capable of absorbing naked DNA
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transformation example w/ mouse
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Griffith
Mouse & pneumonia Capsule has disease –smooth (+) No capsule = no disease – rough (-) Heat –killed (-) Rough & heat killed smooth pneumonia = (+) DNA genes made it sick Removed proteins – still got sick - RNA sick DNA not sick! Competent bacteria |
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Conjugation
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Involves a specialized type of pilus called a sex pilus.
A bacterial cell with a sex pilus (called the donor cell) attaches by means of the sex pilus to another bacterial cell (called the recipient cell). Some genetic material (usually a plasmid) is transferred through the hollow sex pilus from the donor cell to the recipient cell. |
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resistance factor or R-factor
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A plasmid that contains multiple genes for antibiotic resistance
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superbug
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A bacterial cell that receives a R-factor
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In plasmid:
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F + donor of plasmid
F – receiver of plasmid |
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Genetic engineering or recombinant DNA technology
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involves techniques to transfer eucaryotic genes (particularly human genes) into easily cultured cells to manufacture important gene products (mostly proteins)
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Plasmids are frequently used as vehicles for ...
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inserting genes into cells
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examples of many industrial and medical benefits from genetic engineering
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synthesis of antibodies
antibiotics drugs and vaccines also, for synthesis of important enzymes and hormones for treatment of diseases |
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Gene therapy of human diseases involves ...
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the insertion of a normal gene into cells to correct a specific genetic disorder caused by a defective gene
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most common method for inserting genes into cells is...
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Viral delivery
specific viruses are selected to target the DNA of specific cells |
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Genes may someday be regularly prescribed as “drugs” in the treatment of diseases (e.g., autoimmune diseases such as...
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SICKLE CELL ANEMIA, cancer, cystic fibrosis, heart disease, etc
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Sterilization
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Removing all microbial life
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Commercial sterilization
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Killing C. botulinum endospores
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Disinfection
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Removing pathogens
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Antisepsis
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Removing pathogens from living tissue
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Degerming
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Removing microbes from a limited area
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Sanitization
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Lowering microbial counts on eating utensils
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Biocide/germicide
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Kills microbes
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Bacteriostasis
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Inhibiting, not killing, microbes
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selecting an antimicrobial procedure...
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Type of microorganism (Population composition)
Number of microorganisms Environmental conditions -pH -Presence of organic matter -Temperature Risk of infection Concentration of agent Duration of exposure |
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Actions of Microbial Control Agents
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Alteration of membrane permeability
Damage to proteins Damage to nucleic acids |
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Thermal death point (TDP)
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Lowest temperature at which all cells in a culture are killed in 10 min
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Thermal death time (TDT)
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Time during which all cells in a culture are killed
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Decimal Reduction Time (DRT)
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Minutes to kill 90% of a population at a given temperature
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Moist Heat Sterilization
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Moist heat denatures proteins
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Autoclave
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Steam under pressure
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The Autoclave
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Heated water within enclosed vessel forms steam
Steam increases pressure>14 lb/sq in or 101.3 kPa Water boils at higher temp. Standard: 121 deg C at 15 lb/sq in for 15 min Flash: 135 deg C 3 min Prions killed at 132 deg C |
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Steam Sterilization
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Steam must contact item’s surface
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Pasteurization
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Reduces spoilage organisms and pathogens
Equivalent treatments 63°C for 30 min High-temperature short-time: 72°C for 15 sec Ultra-high-temperature: 140°C for <1 sec Thermoduric organisms survive |
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Dry Heat Sterilization
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Kills by oxidation
Dry heat Flaming Incineration Hot-air sterilization |
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Filtration
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HEPA removes microbes >0.3 µm
Membrane filtration removes microbes >0.22 µm |
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Physical Methods of Microbial Control
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Low temperature
High pressure desiccation osmotic pressure |
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Low temperature
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inhibits microbial growth
Refrigeration Deep-freezing Lyophilization |
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High pressure
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denatures proteins
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Desiccation
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prevents metabolism
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Osmotic pressure
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causes plasmolysis
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UV (200-300nm)--non-ionizing
radiation |
damages DNA; causes T-T dimers
little penetration air, surfaces |
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Gamma, X-rays--ionizing
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produces reactive molecules in microbe
heat sensitive materials Foods Measured in absorbed radiation dose (rad) 100 rad=1 Gray |
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Principles of Effective Disinfection
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Concentration of disinfectant
Organic matter pH Time |
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Use-Dilution Test
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Metal rings dipped in test bacteria are dried
Dried cultures are placed in disinfectant for 10 min at 20°C Rings are transferred to culture media to determine whether bacteria survived treatment |
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Phenolics
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Denature proteins, affect membranes
remain active, effective 5% soln kills bacteria skin, neurological damage e.g., cresols, xylenols, Lysol™ (orthophenyl-phenol), triclosan, hexachlorophene |
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Halogens
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Chlorine
Iodine |
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Chlorine
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Oxidizes cell constituents (membranes, DNA, proteins)
disinfectant produces HClOHCl + O water, dairy, food cheap, easy, effective (clean) at 10 mL/L or diluting Clorox (5.25%) |
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Iodine
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linked as iodophore (iodine + organic molecule)
Protein synthesis, cell membranes Antiseptic; e.g. Betadine |
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Alcohols
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Ethanol, isopropanol
Denature proteins, dissolve lipids Require water |
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Alcohols
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Ethanol and Isopropanol
Lipid solvents- Dissolve membrane lipids coagulate proteins Bactericidal, fungicidal, not sporicidal, viricidal (70% solns) Not effective vs naked viruses or endospores Disinfect surfaces Antiseptics Evaporate |
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Heavy Metals
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Ag, Hg, & Cu
Oligodynamic action |
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Ag, Hg, and Cu
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Silver nitrate may be used to prevent gonorrheal ophthalmia neonatorum
Silver sulfadiazine used as a topical cream on burns Copper sulfate is an algicide |
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Oligodynamic action
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Denature proteins
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Peroxides (proteins)
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3% solution hydrogen peroxide
Some bacteria produce catalase; rendering inactive |
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Biguanides (cell membrane)
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e.g. chlorhexidine – skin and mucous membranes
Antiseptics – mixed with detergent or alcohol |
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Aldehydes (proteins)
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inactivate proteins and DNA
glutaraldehyde - sterilize, formaldehyde - preservation |
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Soap - emulsification
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Degerming
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Acid-anionic detergents
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Sanitizing
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Quarternary ammonium compounds (cationic detergents)
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Bactericidal, denature proteins, disrupt plasma membrane
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Chemical Food Preservatives
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organic acids
nitrite prevents endospore germination antibiotics |
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Organic acids
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Inhibit metabolism
Sorbic acid, benzoic acid, and calcium propionate Control molds and bacteria in foods and cosmetics |
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Nitrite prevents ...
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endospore germination
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Antibiotics
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Nisin and natamycin prevent spoilage of cheese
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Gaseous Sterilants
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Denature proteins
Use: Heat-sensitive material Ethylene oxide |
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Plasma
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Free radicals destroy microbes
Use: Tubular instruments |
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Supercritical Fluids
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CO2 with gaseous and liquid properties
Use: Medical implants |
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Antimicrobial
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agents that inhibit the growth or kill microorganisms
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Antibiotics
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Chemicals naturally produced by mold or bacteria that inhibit or kill other microbes
Soil |
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antibiotic Features
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Selective toxicity
Action Spectrum of Activity |
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Selective toxicity
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kills/inhibits microbe without harming host
Usually against microbial pathway not in host Therapeutic index Highest amount drug that can be tolerated by patient Lowest toxic dose/effective dose Higher the index, the less toxic |
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Action
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Bacteriostatic (sulfa drugs – UTI) vs. bacteriocidal
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Spectrum of activity
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Broad vs. Narrow
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Sensitivity determinations
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Minimum inhibitory concentration (MIC)
Minimum bactericidal concentration (MBC) |
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Minimum inhibitory concentration (MIC)
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lowest concentration of drug that prevents growth of organism in vitro
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Minimum bactericidal concentration (MBC)
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lowest concentration that kills 99.9% of bacteria
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Kirby-Bauer Disc Diffusion Tests
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Disk diffusion test (Kirby Bauer antibiotic susceptibility test)
zone of inhibition correlates to susceptibility of organism Resistant, Intermediate, or Susceptible |
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Resistance - mechanisms
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Decrease uptake
alter membrane permeability (transport proteins etc.) Drug-inactivating enzymes e.g. penicillinase Modify target molecule Increase export - efflux pumps |
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Acquisition of resistance
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Spontaneous mutation
Occurs at frequency of ~10-9 vertical evolution affects progeny Acquisition of new genes (gene transfer) horizontal evolution |
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Slowing rate of resistance
Physicians |
Wash hands
No unnecessary prescriptions Narrow spectrum drugs Isolate patients with multidrug resistant infections familiarity with local data |
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Slowing rate of resistance
Public |
Do not demand antibiotics
take as prescribed - full duration, not hoard wash produce & cook meat well only use antibacterial soaps when defenses weakened |
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Inhibition of Cell Wall Synthesis
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Penicillins
Cephalosporins Vancomycin Bacitracin |
