Question

What are microbial cell surfaces? And how are they considered to be important for human being?

Answer 1

Microbial cell surface is basically corelated with the cell membrane of the bacteria. The cell envelope is composed of the plasma membrane and cell wall. The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cytoplasmic membrane.

Gram-positive cell walls are thick and the peptidoglycan ( also known as murein) layer constitutes almost 95% of the cell wall in some gram-positive bacteria and as little as 5-10% of the cell wall in gram-negative bacteria. While Gram-negative cell walls are thin and unlike the gram-positive cell walls, they contain a thin peptidoglycan layer adjacent to the cytoplasmic membrane.

The plasma membrane or bacterial cytoplasmic membrane is composed of a phospholipid bilayer and thus has all of the general functions of a cell membrane such as acting as a permeability barrier for most molecules and serving as the location for the transport of molecules into the cell. As a phospholipid bilayer, the lipid portion of the outer membrane is impermeable to charged molecules. However, channels called porins are present in the outer membrane that allow for passive transport of many ions, sugars and amino acids across the outer membrane.

In the food industry, typical materials which are used in installations are stainless steel, rubber and polytetrafluoro-ethylene (PTFE). Hydrophobic pathogens such as Salmonella spp. and Listeria monocytogenes easily attach to these materials. Microbiological contamination costs the food industry many millions of dollars annually and the research into the processes of microbial adhesion is therefore extremely important. Microbial hydrophobicity plays an important role in processes such as food production, spoilage, etc. due to interactions between microorganisms and food components such as lipids and proteins. For example, species of lactic acid bacteria such as Lactococcus lactis subsp. lactis biov. diacetylactis, which have a key role in the production of yogurts, cheese or sausages, could influence and change the stability of food emulsions. Bacteria with more hydrophobic surfaces have a higher affinity for milk fat and aroma compounds.