Bacterial Habitats in the Antarctic Environment 535 



that low counts of bottom sediments were markedly increased 

 when the medium was supplemented with partially decomposed 

 phytoplankton net hauls before autoclaving. These fragmentary 

 observations on the bacterial content of Antarctic air and sea 

 water confirm the apparent sparsity of bacteria in these habitats 

 when conventional media and procedures are used for cultivation. 



MODIFICATION OF THE ENTERIC MICROFLORA OF 



PYGOSCELID PENGUINS BY PHAEOCYSTIS 



PHYTOPLANKTON BLOOMS 



The failure to detect a sizeable air or sea water microflora as 

 well as the numerous reports on the frequent occurrence of "bac- 

 teriologically sterile" Antarctic animals focused attention on the 

 gastrointestinal microflora of Antarctic birds (16). The presence 

 of 10^ to 10^ organisms per gram in all gastrointestinal segments 

 of some birds while some of the pygoscelid penguins did not 

 contain a detectable microflora in their anterior segments, in- 

 dicated that either the dietary materials contained an inhibitoiy 

 substance or that the diet had a negligible inoculum. Unlike the 

 other birds studied, the pygoscehd penguins did not contain 

 typical lactose-fermenting strains of Escherichia coli. Direct 

 microscopic examinations revealed an abundant dietary micro- 

 flora which could not be cultivated. Antibacterial assays of the 

 euphausid diet of the pygoscelid penguins indicated that the lack 

 of growth was associated with inhibitory activity. An example 

 of the correlation of the number of cultivable bacteria (mainly 

 lactose-fermenting gram-negative organisms) with the antibiotic 

 activity of the ingesta is given in Figure 1, taken from Sieburth 

 (18). The euphausid stomach contents of this gentoo penguin, 

 which were highly inhibitory, failed to yield a detectable micro- 

 flora. The central intestinal contents contained a considerable 

 bacterial population and failed to inhibit the test organisms. Al- 

 though the terminal intestinal contents also contained a large bac- 

 terial population, they were somewhat inhibitory, presumably as 

 a result of bacterial by-products. 



The antibiotic activity of the euphausids (Etiphausia superba) 

 was traced to their stomach contents and then to ph\'toplankton 

 blooms in which a green mucilaginous colonial alga dominated 



