Prosthecochloris aestuarii
Andy Hamilton
Prosthecochloris aestuarii is a green sulfur bacterium that was isolated by Vladimir Gorlenko in 1970.  The green sulfur bacteria are photolithotrophic organisms.  P. aestuarii is strictly anaerobic, found primarily in marine environments.  This bacterium has been isolated from several areas, mostly in the Eastern Hemisphere.

Prosthecochloris aestuarii is a green appendaged organism, as the name implies.  Mostly spherical to ovoid in shape, it has between 10 and 20 appendages per cell.  The appendages are known as prosthecae.  The approximate cell size is 0.5-1.0 um.  This organism has been noted to form a slime capsule around its cells.  Gas vacuoles have not been observed.  P. aestuarii stains gram-negative.  Even with its many appendages, the cell remains nonmotile.  The cells divide by binary fission, however, they do not divide evenly.  The daughter cell is generally smaller than the mother cell.  The bacteria are often connected by one or two filaments after division.  These filaments later develop into prosthecae.  Often the new prosthecae do not separate completely.  This incomplete separation of the appendages leads to chains of cells.  The prosthecae house the chlorosomes used during photosynthesis.

These bacteria are often found in mud that is high in hydrogen sulfide content, usually shallow saline water.  They reside below the purple sulfur bacteria layer.  They are slightly halophilic, optimum NaCl content is about 2-5%.  P. aestuarii also requires vitamin B12 to grow.  Also, they can survive at very high light levels, up to 10,000 lux.  Colonies are generally olive green and lumpy.

P. aestuarii uses sulfide and elemental sulfur as electron donors in the process of photosynthesis.  The elemental sulfur is deposited as extracellular globules.  The deposition of this sulfur causes inoculated cell media to become turbid.  External sulfur globules are later oxidized to sulfate.  This bacterium is capable of receiving its carbon from one source, CO2.  The cells normally use acetate or pyruvate for photoassimilation.  Nitrogen can be obtained from ammonium salts.  Bacteriochlorophyll c is the primary pigment used by P. aestuarii.  Bacteriochlorophyll a is a secondary pigment for this organism’s photosynthetic processes.  Five carotenoids have also been isolated.

 The following pictures are of Prosthecochloris aestuarii:
 

References:

http://www.bsi.vt.edu/facultyfiles/biol_4684/Microbes/greensul.html

Bergey’s Manual p.1688-1690
 

 

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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