546 Marine Microbiology 



were active and able to decompose the fecal material at near 

 freezing temperatures. 



SUMMARY 

 Studies on the gastrointestinal microflora of Antarctic birds 

 indicated a modification and suppression of the microflora of 

 pygoscelid penguins when their euphausid diet was grazing on 

 Phaeocystis pauchetii blooms. The "antibiotic" principle of this 

 alga was isolated, identified as aciylic acid, and its anti-coliform 

 activity in the acidic avian gut was verified. Acr>dic acid, which 

 both enhanced and inhibited the growth of marine bacteria in 

 natural sea water, depending upon concentration, may serve as 

 both a nutrient for planktonic bacteria and as a protective 

 mechanism against bacterial decay of the metabolizing algal cells. 

 The apparent sparsity of marine bacteria in the euphotic zone 

 may reflect a lack of knowledge of the nutrient-temperature re- 

 quirements of bacteria associated with the phytoplankton. Pen- 

 guin feces apparently underwent bacterial decomposition at am- 

 bient temperatures as shown by changes in pH, antibacterial 

 activity and a transition from a fecal to a soil microflora in ma- 

 terial at various stages of decomposition. 



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