Bacterial Habitats in the Antarctic Environment 545 



parent sparsity of marine bacteria may be due to the use of ani- 

 mal peptone media as well as elevated temperatures and short 

 incubation periods commonly used in shipboard surveys (7), 

 rather than to a lack of a bacteria. 



Waksman (27) has pointed out that under natural conditions 

 antibiotics play no significant role except when the habitat is 

 relatively simplified such as within the gastrointestinal tract of 

 animals. The acidic gut of the pygoscelid penguins was optimal 

 for the detection of the acid potentiated antibiotic activity of 

 acrylic acid from the alga Phaeocysfis pouchetii. However the 

 acidic nature of phytoplankton net hauls and the concentration 

 of small carbon acids produced by marine algae indicated that the 

 micro-interface of the algal cells may have a sufficiently acidic 

 reaction even in sea water to permit these acids to act as bac- 

 teriostatic compounds. Such a phenomenon might protect metabo- 

 lizing algal cells against bacterial attachment and decay. 



The studies on fecal and "soil" material from penguin rook- 

 eries on three different islands in the South Shetland group indi- 

 cate that bacterial decomposition does occur at the cool ambient 

 summer temperatures. Studies to date, such as that by Straka 

 and Stokes ( 26 ) , report the use of frozen samples of undetennined 

 age and nature to enumerate and isolate psvchrotolerant micro- 

 organisms. The acidic feces which contained a variable fecal flora 

 apparently underwent rapid bacterial decomposition as indicated 

 by the alkaline reaction and antibacterial activity (presumably 

 as a result of ammonia formation) of fresh guano in occupied 

 nests. Nest guano had a "fecal," mixed "fecal and soil," or "soil" 

 flora depending upon age and nesting activity in the rookery. 

 Various organisms such as Sarcina and Micrococci which are 

 minor components of the fecal flora became dominant. Old nest 

 guano, soil and soil "humus" which was acidic in nature con- 

 tained organisms similar to Mycococcus dlhus subsp. lactis and 

 Bacillus tinakiensis (8). Many of the isolates required incubation 

 temperatures below 20 C after the initial subculture. Changes 

 in pH and antibacterial activity and a transition from a "fecal" 

 to a "soil" flora in material of various ages and states of decay in- 

 dicated that at least certain components of the bacterial flora 



