Lactobacillus Brevis - Microbial Physiology

Microbial Physiology

As a bacterium there are some physical attributes that are common for all bacteria. Gram-positive bacteria consists of an external plasma membrane, followed by periplasmic space and finally a peptidoglycan layer, which faces the interior of the bacteria. The external plasma membrane is very important for bacteria because this is how cells recognize the possible pathogenesis of the bacteria. Peptidoglycan is also called murin and is made up of a series of sugars. Within gram-positive bacteria the peptidoglycan layer is much thicker than gram-negative bacteria. The actual lattice that comprises peptidoglycan is referred to as the S-layer; this lattice is linked to the peptidoglycan layer. Unfortunately, the S-layer is normally lost when processing the bacteria under laboratory conditions, which can affect measuring adhesion. When the S-layer is dissolved with high concentration levels of substances that break down hydrogen bonds the S-layers have a survival time of about 20 minutes with each generation. L.brevis contains approximately two promotors within this area, meaning that there is significant transcription of the S-layer by high levels of transcribing of the sIpA gene. SipA is a gene that has been found to aid in the coding for the production of murin (peptidoglycan) within the bacteria. The purpose of transcription is to copy DNA into a mRNA, which is used to create proteins. The promoter is used during transcription to identify the appropriate location to begin transcribing. Within probiotics it is actually the S-layer that attaches to the cellular wall of the gastrointestinal tract