696 Marine Microbiology 



of microorganisms does not necessarily reflect a proportional ac- 

 tivity in the transformations implied by their designations, nor 

 does it exclude this." (20) Furthermore there would be little 

 useful application of laboratory data on the nutritional require- 

 ments of bacteria from deep sea sources if incubation tempera- 

 tures and atmospheric pressures inactivate constitutive enzymes 

 to induce certain nutritional deficiencies. It was of interest there- 

 fore to observe the similarity in the distributions of nutritional 

 groups in sediment bacteria from 100 m and in those from 2400 

 m. Sediments from both localities were fine grey muds. 



The relevance of serious sampling problems in the primary 

 isolation of organisms is self-evident. Discrepancies between plate 

 and direct counts would be of small consequence in the present 

 method of analysing bacterial populations if all components were 

 proportionately represented among isolates. Although an isola- 

 tion medium enriched with materials imitating the natural en- 

 vironment has many theoretical attractions, any "non-selective" 

 capacity can by no means be assured. It is also clear that the 

 method is of little value in the classification or taxonomic sense 

 for there is unlikely to be an unequivocal difterentiation between 

 organisms merely according to tlieir growth response in tlie stan- 

 dard media. 



The technique developed by Lochhead does provide however 

 a means of comparing some of the potential functional relations 

 of marine bacteria in a variety of ecological circumstances. De- 

 spite limitations of the present data, there are indications that 

 outstanding distinctions between marine bacterial populations in 

 regard to their nutritional activity may be related to differences 

 between their particular environmental associations, and it is 

 felt that these preliminary studies justify extension. Farther in- 

 vestigations may be helpful in resolving some of the less well 

 known implications of heterotrophic bacterial activity, in par- 

 ticular, processes involving the utilization, production and ex- 

 change of critical nutrients within marine ecosystems. 



REFERENCES 



1. Allen, M. B.: Excretion of organic compounds by Chlamydomonas. 

 Arch. Mikrobiol. 24:163-168, 1956. 



