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94 Cards in this Set
- Front
- Back
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What three shapes do most bacteria assume?
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Cocci (spheres)
Bacilli (rods) Spirochetes (spirals) |
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What are three configurations of cocci?
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Staphylococci (clusters)
Streptococci (chains) diplococci (doublets) |
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What are pleomorphic bacteria?
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Bacteria that do not have a defined shape.
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What is an example of a pleomorphic bacteria?
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Mycoplasma; it lacks a cell wall.
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What is the average size of a bacterium?
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1 to 5 microns in diameter.
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How does the diameter of a bacterium compare to viruses and eukaryotic cells?
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100 times larger than a virus
10 times smaller than a eukaryotic cell |
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What is the cell envelope?
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The material external to and enclosing the cytoplasm?
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What are the two main functional layers of the cell envelope?
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Cell membrane and cell wall.
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What is the cell membrane made of?
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Phospholipid bilayer and proteins
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What is the main component of the cell wall?
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Peptidoglycan (murein), which forms a cross-linked mesh.
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What is the "peptido" portion of the peptidoglycan made of ?
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Short string of amino acids.
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What is the 'glycan' portion of the peptidoglycan made of ?
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Alternating monosaccharides
N-acetylglucosamine (NAG) N-acetlymuramic acid (NAM) forming the back bone of the mesh. |
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How is the peptidoglycan mesh formed?
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Amino acids cross-link glycan backbones at NAM subunits.
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What is the purpose of the peptidoglycan mesh?
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Determines cell shape and size and provides stability against lysis.
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Which two bacterial genera do not contain peptidoglycan?
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Mycoplasma
Chlamydia |
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What stain is used for microscopic identification of peptidoglycan in bacterial cell walls?
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Gram stain
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What two categories of bacteria are delineated by this stain?
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Gram-positive, which appear purple (thick wall retains dye)
Gram-negative, which appear pink (thin wall, dye washes out) |
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What are the five steps of a gram stain reaction?
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1) Heat fix specimen to slide, add crystal violet, let react for 1 minute, rinse slide.
2) Add iodine, let react for 1 minute, rinse slide. 3) Decolorize with acetone or alcohol, rinse with water. 4) Add safranin counterstain, rinse with water. 5) Blot dry, and visualize under microscope. |
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What are the two components of a Gram-positive cell wall?
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Teichoic acid and a thick, multilayered peptidoglycan layer
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What is teichoic acid?
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Glycerol polymers that are bonded covalently to peptidoglycan lipids.
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Why is teichoic acid significant?
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1) Involved in adherence of bacteria to host cells.
2) Serves as a cell surface antigen 3) Promotes inflammatory response. |
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What are the five components of a G- cell wall in order from external to internal layer?
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1) Outer membrane
2) Lipoprotein 3) thin peptidoglycan layer 4) Periplasmic space 5) Inner (cytoplasmic) membrane |
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What makes up the outer membrane?
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Lipid bilayer with embedded lipopolysaccharides (LPS) and proteins
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What is the antigenic portion of the lipopolysaccharide of the outer membrane?
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O-polysaccharide
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Why is the antigenic portion of the lipopolysaccharide of the outer membrane important?
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Highly antigenic virulence factor used to identify species and strains.
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What is the toxic lipid portion of the lipopolysaccharide of the outer membrane?
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Lipid A (endotoxin)
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What makes Lipid A virulent to humans?
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Activates complement and coagulation pathways and induces secretion of tumor necrosis factor (TNF) and interleukin-1 (IL-1)
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What does lipoprotein do?
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Links the peptidoglycan with the outer membrane
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What is the periplasmic space?
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Space between the inner and outer membranes.
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What is contained within the periplasmic space?
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1) Peptidoglycan layer
2) Penicillin-binding proteins 3) Hydrolytic enzymes (including beta lactamases) |
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What are three external components of the cell envelope?
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1) Polysaccharide coating
2) Flagella 3) Pili |
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What is the adhesive, viscous polysaccharide coating external to the cell wall?
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Capsule or glycocalyx
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What is the coating called if it is tightly bound to the cell and organized?
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Capsule
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What is the coating called if it is loosely bound to the cell and amorphous?
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glycocalyx
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What is the purpose of a capsule of glycocalyx?
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1) Adherence to surafaces
2) Protection from antibodies and phagocytosis 3) Barrier against some antibiotics. |
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What laboratory test is used to detect organism with a capsule?
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Quellung reaction
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How is a quellung reaction performed?
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Mix antiserum with capsular polysaccharides, resulting in swelling of the capsule.
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What are two kinds of appendages that project from the cell wall?
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Flagella and pili
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What are some characteristics of flagella and pili?
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1) Flagella are highly antigenic tubular structures that rotate to propel bacteria toward chemotactic stimuli
2) Pili promote attachment to other cells and are shorter than flagella. |
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What are the components of the cytoplasm?
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Amorphous fluid with enzymes, ions, metabolites, ribosomes and a nucleoid.
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What is the bacterial nucleoid?
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A concentration of single circular double-stranded deoxyribonucleic acid (DNA), ribonucleic acid (RNA), RNA polymerase, and other proteins without a nuclear membrane.
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What is the purpose of a ribosome?
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protein synthesis
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What are the ribosomal subunits in bacteria?
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30S and 50S subunits, which combine to form a 70S ribosome.
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Why are bacterial ribosomes important in antibiotic treatment?
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Antibiotics may be specifically targeted for bacterial ribosomes, which are different from human ribosomes that combine to form 80S complexes, thereby impairing protein synthesis and causing death or stasis of bacteria without affecting human cells.
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What are plasmids?
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Small, circular, double-stranded DNA molecules capable of self-replication frequently containing genes that convey antibiotic resistance or toxin protuction.
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How are plasmids different than transposons?
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Plasmids are capable of self-replication.
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What are spores?
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Metabolically dormant, protected bodies highly resistant to heat, desiccation, and chemicals, and are capable of germinating and establishing colonies
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Why are spores formed?
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Adaptive mechanism to survive adverse environments such as excess heat, cold, or conditions lacking sufficient nutrients.
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What confers resistance to heat?
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Thick keratin coat containing calcium dipicolinate and a low water content.
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When do spores germinate?
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When they are exposed to appropriate nutrients and water.
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Which two G+ rods produce spores?
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Bacillus
Clostridium |
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How do bacteria reproduce?
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Binary fission
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What are the four stages of growth?
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1) Lag phase
2) Log phase 3) Stationary phase 4) Death phase |
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Which phase corresponds with cells adapting to a new environment?
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Lag phase
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Which phase corresponds with constant rate of cell doubling?
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Log phase
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Which phase corresponds with balance of bacterial rowth and death?
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Stationary phase
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Which phase corresponds with accumulation of toxic metabolites or lack of nutrients?
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Death phase
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What are heterotrophs?
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Bacteria requiring organic compounds for growth.
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Which element do all heterotrophs require for growth?
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Organic carbon
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What are autotrophs?
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Bacteria capable of synthesizing organic compounds from carbon dioxide, eliminating a need for preformed organic compounds for growth.
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What are obligate intracellular bacteria?
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Bacteria that must invade host cells in order to survive and replicate.
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Name four obligate intracellular bacteria.
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1) Rickettsia
2) Chlamydia 3) Coxiella 4) Ehrlichia |
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What are facultative intracellular bacteria?
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Bacteria that can survive either inside or outside a cell.
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Name seven facultative intracellular bacteria.
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1) Listeria monocytogenes
2) Salmonella typhi 3) Yersinia 4) Legionella 5) Brucella 6) Francisella tularensis 7) Mycobacterium |
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What gas requirement can be used to categorize bacteria?
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Dependence for oxygen
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What are the bacteria that can grow in the presence of oxygen called?
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Aerobes
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What are bacteria that require oxygen for growth called?
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Obligate aerobes
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Why do obligate aerobes require oxygen?
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Must use oxygen as the terminal electron acceptor in energy production.
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What are bacteria that grow in the presence or absence of oxygen called?
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Facultative anaerobes
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What is the oxygen preference of facultative anaerobes?
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True facultative anaerobes prefer to use oxygen as the terminal electron acceptor but do not require it for survival.
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What are bacteria that require or tolerate oxygen at lower than atmospheric pressure called?
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Microaerophilic
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What are bacteria that prefer or require carbon dioxide at highr than atmospheric pressures called?
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Capnophilic
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What is an example of a capnophilic bacteria?
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Neisseria
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What are bacteria that can grow without oxygen called?
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Anaerobes
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What are bacteria that grow only in the absence of oxygen called?
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Anaerobes
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What are bacteria that can grow only in the absence of oxygen called?
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Obligate anaerobes
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What enzymes are present in aerobes that are not present in anaerobes?
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Either superoxide dismutase, catalase, peroxidase, or all three.
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What reaction does superoxide dismutase catalyze?
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Conversion of free radical superoxide and hydrogen to hydrogen peroxide and oxygen.
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What reaction does catalase catalyze?
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Conversion of hydrogen peroxide to water and oxygen.
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What reaction does peroxidase catalyze?
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Conversion of hydrogen peroxide to water and a hydroxide compound.
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Give examples of obligate aerobes.
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Pseudomonas spp
Mycobacterium tuberculosis Mycoplasma spp Nocardia Bordetella pertussis Francisella tularensis Brucella spp |
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Give moderate obligate anaerobes examples.
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Bacteroides fragilis
Clostridium perfringens Fusobacterium nucleatum |
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Give examples of strict obligate anaerobes.
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Clostridium haemolyticum
Clostridium tetani Clostridium difficile Clostridium novyi type B Treponema denticola: Prevotella-Porphyromonas |
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Give examples of facultative anaerobes?
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Escherichia coli
Enterococcus, Salmonella Shigella Staphylococcus aureas, coagulative negative Staphyloccos spp Yersinia Haemorphilus spp Actinobacillus spp Bacillus anthracis Bacillus cereus Corynebacterium spp Listeria monocytogenes Erysipelothrix |
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Give examples of microaerophilic bacteria.
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Camphylobacter ejuni
Helicobacter pylori Streptococcus pyogenes Streptococcus pneumoniae |
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What are the three categories of metabolism in bacteria?
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Aerobic respiration
Anaerobic respiration Fermentation |
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What form of energy is produced in bacteria?
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Adenosine triphosphate (ATP)
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How is energy produced by respiration?
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Oxidative phosphorylation
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Where does respiration take place?
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Cell membrane, because prokaryotic bacterial cells lack mitochondria and other organelles.
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What compound serves as the final electron acceptor in electron chain transport in aerobic respiration?
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Oxygen
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What compound serves as the final electron acceptor in electron chain transport in anaerobic respiration?
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Inorganic compounds, e.g. nitrate, sulfate, and carbon dioxide.
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What is fermentation?
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Breakdown of monosaccharide to pyruvic acid which is usually converted to lactic acid or other organic end products.
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How is energy produced by fermentation?
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Substrate-level phosphorylation
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What compound serves as the final electron transporter in fermentation?
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Organic compounds that are formed from the breakdown of monosaccharides.
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