Thursday, July 25, 2013

Opportunistic Bacteria

Bacterial Spores

Cells are of microscopic size because of their inefficient means to distribute resources internally.  The processes providing for life require a continuous supply of molecules, such as oxygen, that are absorbed by the cell’s outer membrane.  Relying largely on diffusing critical resources across a cell’s interior to reach metabolizing sites, makes it nearly impossible for a cell to become the size required to be seen with the unaided eye.

Most bacteria are many times smaller than are the cells found in the tissues of plants and animals.  Bacterial, or prokaryotic cells, do not have the complex interior structures found in the eukaryoticcells that make up multicellular organisms.  Bacteria’s reliance on their more elemental structure does not, by itself, explain their minuscule size.  A look at the advantages gained by drastically reducing the cell’s volume from its theoretical limit provides clues into the harsh nature of the bacterial environment. 

Diminishing the cell’s size aids in its relative capacity to absorb nutrients from its surroundings.  The absorption area of the cell increases proportionally as its volume is reduced.  A resource becomes more plentiful, while there is a corresponding decreased need for it, due to the cell’s smaller size.   This provides the basis for increased metabolism and a higher rate for synthesizing proteins and nucleic acids that are critical to the cell’s growth.  Bacterial cells often divide into two sister cells once they reach twice their original size.  Bacteria are notorious for their potential for exponential growth.  Some species, under optimal conditions, have been known to produce an entirely new generation within the space of twenty minutes.  A time span of several hours is more likely but the rate of reproduction is still dynamic when compared with the population growth demonstrated by Eukaryota cells, such as the amoeba.

Rapid population growth is usually the strategy of a species that also suffers a very high mortality rate.  Bacteria behave in an opportunistic manner, indicating conditions needed for their survival may have a very short time-frame   An instance of rotting plant or animal tissue in an otherwise dry environment makes available a rich organic soup to a community of bacteria.  The bacterial population quickly explodes in number.  They thrive only briefly, though, before the intense sun exhausts their world of moisture and other unfavorable environmental factors take hold.  Individual bacteria react to their increasingly hostile surroundings by synthesizing a shell that encloses and protects their molecule of DNA.  This is a spore, but unlike the spores used by fungus for reproduction, this structure is a lifeboat with the singular purpose of survival.  Its hard outer casing resists the fatal effects of high temperatures, dryness, harsh chemicals or being frozen in liquid, any of which would lead to the destruction of the delicate DNA molecule.  The spore is at rest, void of the many ingredients needed for metabolism, so it exists in a state of suspended animation. 

Only when a life sustaining environment is once again detected, will the encapsulated DNA instigate chemical reactions that lead to the full restoration of life processes.  It may be a very long wait before wind makes the spore airborne or a stream from rainfall carry it to a new opportunity to prosper – fallen fruit rotting beneath a tree or an open wound in a dying animal.  The microbial life form resumes its organizational efforts that keep it one important step above the level of death… breaking chemical bonds to generate the energy needed to power its synthesis of magnificently complicated molecules, that are used to build structures to enable life, and structures to insure its perpetual preservation, in copy after succeeding copy, throughout the long history of life on this planet, Earth.

Biology Topics:

Eukaryotic Cell

Protein Creation

Molecular Basis of Life

Living - Why?

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