Energy type

The determination of the standard energetics (or standard respiratory ) of a Bactérie consists of the determination of the report/ratio which this bacterium with the Dioxygène has (O₂, of the air).

A Bactérie has specific respiratory needs. It is:

Aerobic strict: it needs Oxygène to live and develop
aéro-anaerobe optional: the presence of oxygen is preferable for the development of the bacterium but it can occur some.
Anaerobic microphone-aérophile
strict: the presence of oxygen is Létale for the bacterium.

Determination of the energy type

It is a question of cultivating the bacteria to be studied in a Culture medium containing a Gradient partial Pression oxygen.

Culture medium used

One uses the medium meat cast liver in long fine tubes (of the tubes of Provost of 9 X 180 mm). This medium, after regeneration, is maintained liquid and in Surfusion to expel gases dissolved in the Gélose.

Technique

To regenerate the medium while placing it at the Bain-marie during 30 min with 100 °C then to maintain in superfusion 10 min with 50 °C.
To sow in gimlet of green bottom the top using a Pasteur pipette buttoned.
To solidify with cool water and to incubate with 37 °C.

Solid, the medium has a gradient of concentration in O₂ where it is more abundant on the surface. The place where the Colonies in the tube are, determines the energy type:

has Colonies in all the tube: bacteria aéro-anaerobes
B Colonies in top of the tube: strict aerobic bacteria
C Colonies in top of the tube, slightly under surface: bacteria microphone-aérophiles
D Colonies in bottom of the tube: strict anaerobic bacteria

Various energy types

According to Provost, there exist 7 energy types. But some being rather rare, we will quote only 4 of them.

Type I known as strict anaerobe

The strict anaerobic bacteria cultivate themselves only safe from the air. The majority of the bacteria of this type are able to support the atmosphere a certain time. Others are extremely oxygénosensibles.

Type II known as microaérophile

The bacteria microaérophiles are much rarer. They are bacteria whose Enzyme S (in particular the Catalase) function correctly only under one reduced pressure of Dioxygène.

Their energy is produced by Fermentation. In the presence of Dioxygène, they can use the direct oxydative way but, deprived of system destroying it (Catalase or Peroxydase), the accumulating Hydrogen peroxide becomes Bactéricide. Examples: Clostridium , Fusobacterium , Bacteroides .

Type VI gathering 2 sub-types: optional aerobe and optional anaerobe

The optional aerobic bacteria can use all the energy ways or limit themselves to principal. Examples: Staphylococcus , Enterobacteriaceae .

The optional anaerobic bacteria can use only fermentations. They are bacteria Anoxybotique S. Exemple: Streptococcus

In practice, it is difficult to distinguish the two energy types. One gathers these bacteria under the aéro-anaerobe type.

Type VII known as strict aerobe

The strict aerobic bacteria cultivate themselves only in the presence of air and breathes in aerobiosis by oxydative phosphorylation. Examples: Pseudomonas , Micrococcus .

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