Lab report on Enterobacteriaceae and other Gram Negative Rods. Description of certain bacteria and tests used to identify them

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Identification System for Enterobacteriaceae and other Gram Negative Rods.


The culture that I was given was culture B. The 7-digit numerical profile of my organism was 3604132. This organism is known as citrobater freudndii.



Escherichia consist of either singular or pairs of straight rods with a diameter of 1.1- 1.5mm and a length of 2.0-6.0 mm. In the majority of strains they have a capsule or a microcapsule present and their cell walls are gram negative.

They are either motile, from the presence of peritrichous flagellum or non motile.

They are facultatively anaerobic and are defined as being a chemoorganotroph.

Escherichia prefer an optimum temperature of 37 °C.

They catabolise D-glucose and other carbohydrates to form acid and gases.

Escherichia are opportunistic pathogens usually associated with wound infection.


Consisting of straight rods they have a diameter of 1 mm and a length of 2-6 mm.

They are found either singularly or in pairs and stain as gram negative. They are usually motile due to peritrichous flagella.

As with Escherichia, Citrobacter is both facultatively anaerobic and a chemoorganotroph. They also have an optimum temperature of 37 °C.

Citrobacter release acid and gases from catabolising D-glucose. They reduce nitrates and usually ferment L-arabinose, cellubio, glycerol and maltose.

They occur in human and animal faeces and they are opportunistic pathogens.


With a diameter of 0.6 mm and a length of 1.2-3 mm long they consist as straight rods. They are gram negative and all are motile by peritrichous flagella except for E.asburiae. They are facultatively anaerobic and chemoorganotrophic. They survive best at a temperature between 30-37 °C. They also catabolise D-glucose to produce acid and gases as bi-products.

Malonate is usually utilised and gelatine if liquefied with 3-14 days in most strains.

Enterobacter occurs in fresh...