BIOFILMS
Despite the simplistic, and rather humble, appearance of prokaryotic cells, they are quite sophisticated and well-equipped to maintain homeostasis despite changes in their external environment. All living organisms, even tiny prokaryotic lifeforms, must adjust to changes in temperature, sunlight, pH, salinity, osmotic pressure or toxic substances in their environment. Failure to do so can lead to death or other serious consequences for the organism.
Maintaining Homeostasis
In conditions of low light, certain photosynthetic microorganisms can increase their production of chlorophyll to make better use of the limited sunlight available. Some bacteria even exhibit sophisticated defense response against antibiotics! Bacteria can secrete antibiotic-killing compounds that function to break down the cell wall or cell membrane of the antibiotic.
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We also observe cooperation between bacteria cells that form a biofilm.
Very few bacteria are live independently. 99% of bacteria live as part of a larger entity called a "biofilm". Biofilms are of special interest, because they display many of the characteristics of multicellular organisms. The cells communicate to each other through chemical signaling and even become physically attached to each other and to a surface using interlacing polymers they the cells secrete.
- Stage 1: Initial Attachment. A free-floating bacteria reversibly attaches to a surface.
- Stage 2: Irreversible Attachment. The small colony irreversibly anchors itself to the surface through the cell adhesion molecules and polysaccharides they secrete.
- Stage 3: Maturation I. The adhesion site get more complex and diverse and cell division begins along with cell recruitment.
- Stage 4: Maturation II. The biofilm has reach full maturity. The matrix envelopes the biofilm an provides protection from harmful elements including antibiotics.
- Stage 5: Dispersion. Occasionally, single cells will be released from the biofilm during cell division. These cells will be dispersed and will be able to form to biofilms.
Quorum Sensing
Bacteria cells function very differently when they are together with other cells. The bacteria cells can sense ( hence ... "quorum sensing") the density of the population that they are a part of. As the population density increases, the bacteria cells respond by changing their gene expression.
For example, bacteria cells that are part of a high-density population, such as a biofilm, will change their phenotype to fit whatever the needs of the biofilm as a whole are at that time. WOW!
For example, bacteria cells that are part of a high-density population, such as a biofilm, will change their phenotype to fit whatever the needs of the biofilm as a whole are at that time. WOW!