42 Marine Microbiology 



previous failures to cultivate bacteria there were due to lack of 

 knowledge of regulating mechanisms rather than to an actual 

 scarcity of organisms. For instance, a particular group of pen- 

 guins, which feed on euphausids, did not contain, by culture tests, 

 any detectable microflora in their anterior gut segments. Direct 

 microscopic examination however, revealed an abundance of 

 organisms. Eventually an antibacterial substance was traced, first 

 to the diet-organisms, then to their stomachs, and finally to 

 phytoplanton blooms in which a particular alga dominated, on 

 which the euphausids had been feeding. The principle was iso- 

 lated and identified as acrylic acid and its antibiotic effect on 

 E. coli has been verified. Penguin faeces which form guano de- 

 posits at rookeries apparently undergo bacterial decomposition at 

 the ambient temperature of 5 C to yield a "humus" which sup- 

 ports a bryophytic flora. In an attempt to characterize bacterial 

 changes, penguin guano was examined in various stages of de- 

 composition. Media inoculated with freshly voided faeces initially 

 became alkaline, and then with further decomposition an acid 

 reaction set in, eventually reaching pH 4. With time there was a 

 gradual transition from a faecal to a soil microflora. 



Lebedeva and colleagues from the Sevastopol Biological Sta- 

 tion (Chapter 50) have made cultures of the micro-organisms 

 from different regions of the Mediterranean Sea. About 40 ml of 

 water are passed through a membrane filter, and eventually cul- 

 tured on a medium of agar and fish meal hydrolysate which had 

 been digested with trypsin. This brings up colonies capable of de- 

 composing albuminates. Regional differences were found, the lar- 

 gest counts being recorded from the Strait of Otranto and the 

 Strait of Tunis. The various seas in the central part of the Medi- 

 terranean gave lesser values. No relation could be found between 

 the quantitative distribution of microorganisms at different 

 depths and the vertical distribution of temperature and salinity. 

 The distribution of maximal and minimal counts of bacteria with 

 depth suggests that the whole water mass of the Mediterranean 

 has a general pattern of stratification. Very high counts were ob- 

 served at stations near the mouth of the Nile, and it was possible 

 to follow the penetration of Nile water out into the open sea for 

 at least forty miles, and to trace its north-easterly direction, on 



