Gram Negative Bacteria Lab Report

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The objective of this lab was to isolate and identify an unknown Gram positive and Gram negative bacteria through the use of various microbiological techniques. The identification of the genus and species for the unknown culture should be obtained based on the characteristics for Gram positive and Gram negative bacteria. Bacteria are prokaryotic microorganisms that lack a nucleus and therefore all its genetic information is stored in the cytoplasm of the cell. The bacterial cell envelope protects the cell and consists of a cell membrane(s) and a cell wall. The cell membrane surrounds the cytoplasm is composed a phospholipid bilayer which contains hydrophobic membrane proteins (Slonczewski & Foster, 2015). The cell wall that protects the cell …show more content…
The cell wall is composed of several layers of peptidoglycan which are held together by teichoic acids, which gives the cell wall a negative charge. Teichoic acids also consists of lipotechoic acids which have a lipid component that attaches to the cell membrane (Slonczewski & Foster, 2015). Gram positive bacteria reproduce through binary fission where one parental cell splits into two equal daughter cells and contains all the information needed to survive (Department of Biological Sciences, 2015). However certain Gram positive bacteria are able to form endospores as a survival strategy through a process called sporulation, which happens when the bacteria experiences environmental stress, such as starvation due to limited nutrient sources. Sporulation is an asymmetrical cell division that produces an endospore which is extremely resistant to heat and desiccation and will lay dormant until it is germinated (Slonczewski & Foster, 2015). Gram positive bacteria is a chemoorganoautotroph, which means that it obtains energy and carbon sources through the oxidation of organic compounds, such as sugar, for growth and development (Slonczewski & Foster, …show more content…
The thin cell wall is composed of one to two layers of peptidoglycan which is covered by an outer membrane. The outer membrane has a high lipid content consisting of outward facing phospholipids called lipopolysaccharide and inward facing lipoproteins. The inward facing lipoproteins face in towards the periplasm and connects the outer membrane to the cell wall. The inward facing layer of the outer membrane has very similar composition to the inner membrane. The outer membrane also contains proteins called porins, which controls the diffusion of sugar, ions, and amino acids. Gram negative bacteria usually display a cell shape that is cocci, bacilli, or coccobacilli. Gram negative organisms reproduce through binary fission. There are some Gram negative species that as individuals can move together and aggregate into a rising mound called a fruiting body, which is triggered from starvation. Within the fruiting the bacteria then differentiates into a spherical spore which is then released into the surroundings to look for new sources of nutrients (Slonczewski & Foster, 2015). Gram negative bacteria can be phototrophic or chemolithoautotrophic. Phototrophic organisms obtain energy by absorbing light which triggers chemical reactions while chemolithoautrophs gain energy by oxidizing inorganic substances (Slonczewski & Foster,

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