Isolating and identifying unknown bacteria
is essential to microbiology. In a research setting, an identified isolate can
be studied for its role in important biological mechanisms. The research team
at the University of Tübingen led by Professor Friedrich Götz wanted to compare
the immune response to a commensal bacteria species to that of a non-commensal
bacteria species. By isolating strains of the commensal Staphylococcus aureus and Staphylococcus
epidermidis, both naturally found in the human flora, and the non-commensal
Staphylococcus carnosus, the
researchers discovered that the commensal species induced a much lower immune
response than the non-commensal species (Nguyen et al., 2017). Aside from its use in the field of research, bacterial
isolation and identification also has its uses in the medical industry in which
an isolated pathogen from a patient could identify the cause for disease and determine
subsequent treatment, and in the food industry where an isolated microbe can be
identified as the cause of contamination. Therefore, the isolation and
identification of bacteria plays an integral role in maintaining our health and
understanding how we function.

In this experiment, the isolation and
identification of two bacterial samples will be demonstrated using various
tests. Isolate A will be derived from an anal sample from the researcher.
Isolate B will be extracted from a soil sample. For each of these isolates, the
sample will be streaked on an ajar plate containing the appropriate solid media
until a pure culture is obtained. A Gram stain will then be performed to
determine the presence or absence of a cell wall. Cells that test gram-positive
display a violet color when dyed because this color is retained in species with
a peptidoglycan cell wall. Cells that test gram-negative cannot retain the
violet color due to the absence of a cell wall and instead display a pink color
from another subsequent dye. From there, a catalase test, an oxidase test, a
phenol red test, a minimal media test, and a fluorescent pigment test will be
performed to determine catalase presence, cytochrome c oxidase presence, glucose
fermentation, survival in the absence of added nutrients, and pigment secretion,
respectively. By collecting data on all of these characteristics, the bacterial
species of Isolate A and B can be identified using the ABA DABA chart. 

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