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Identification of unknown bacteria: E coli and S epidermidis

Unknown Project: Identification of E. Coli and S. epidermidis from Unknown #20
Praise Agu
MCB2010 Laboratory
Professor Nerka Vujovic
August 13, 2020

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Identification of unknown bacteria: E coli and S epidermidis

Table of Contents

Abstract ..................................................................... 3Error! Bookmark not defined.
Introduction ........................................................................................................................ 6
Materials and Methods ....................................................................................................... 8
Observation &Results ....................................................................................................... 16
Discussion .......................................................................................................................... 17
References ......................................................................................................................... 18

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Identification of unknown bacteria: E coli and S epidermidis

Abstract
The project for identifying unknown organism was requested to be done by the
students to learns about the characteristics of particular bacterial organisms. The
students were given one numbered microcentrifuge containing two different bacteria, one
coliform and one non-coliform. We received a list of three coliform bacteria and nine
non-coliform bacteria to discover/ narrow down our unknown. This project is an objective
type of study and is based on inquires. The objective is for students to plan an
investigation by carrying out a variety of essential tests to produce scientific data in
support of the unknown and thus identify the unknown bacteria. Essentially, students are
to provide data and support to eliminate the other species on the list of coliform and noncoliform in order to identify their unknown species. The students create a dichotomous
key (Figure 1) to assist in correctly identifying unknown bacteria. In the laboratory setting
usual set of identification test performed on an unknown specimen are gram staining,
culture on different media, various biochemical tests. The goal of this study is for the
respective students to get a detailed experimental knowledge on how to identify an
unknown bacterial species, get a closer look at important bacterial species that are
relevant for disease diagnosis in humans, food contamination studies and other. The two
unknown bacteria discussed in this lab report are Escherichia Coli and staphylococcus
epidermidis.

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Identification of unknown bacteria: E coli and S epidermidis

Introduction
Microorganisms are living organisms of microscopical size. The size of a bacteria is
measured in units of a micron. Depending on their shape, bacteria are classified into
several types –
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Cocci – oval or spherical in shape such as staphylococcus, streptococcus

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Bacilli – rod shaped cells. Some of these have peculiar shapes that are
described as

1.

Coccobacilli – length is almost same as width. E.g. Brucella.

2.

Streptobacilli – arranged in chains. E.g. Streptobacilli.

3.

Cuneiform pattern – arranged at angles. E.g. Corynebacterium.

4.

Comma-shaped – curved appearance. E.g. vibrio

5.

Spirilla – rigid spirals. E.g. spirillum
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Spirochetes – coiled shaped such as Treponema species.

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Actinomycetes – these are branching filame...