686 Mamie Microbiology 



proportion of the microflora indigenous to oceans and sediments. 

 Investigations of the latter groups have been hampered by tech- 

 nical and theoretical difficulties in their isolation and the lack of 

 appropriate criteria for their classification. 



The majority of forms cultivated from marine sources have 

 been described as Gram-negative asporogenous short rods, many 

 of them motile and proteolytic, possessing a relatively low degree 

 of biochemical activity as judged by standard laboratory tests 

 (8, 26). Yet direct microscopic observations of planktonic bac- 

 teria indicate the existence of a variety of morphological types 

 which cannot be reproduced in the laboratory by traditional cul- 

 tural methods ( 12 ) . Using similar direct techniques, Jannasch 

 (9) discussed evidence for the existence of a component of the 

 microflora of natural waters consisting of "dwarf" forms that 

 escape detection until supplied with concentrated nutrients. He 

 thus extended for aquatic systems the considerations of Winograd- 

 sky (24), who viewed the bacterial flora of soils in two categories, 

 autochthenous and zymogenous. The autochthenous (indigen- 

 ous) organisms, whose numbers remain fairly constant, were 

 regarded to be physiologically unreactive, and characteristic of 

 soils poorly supplied with fermentable substances and possibly 

 taking part in the slow combustion of humic constituents of soils. 

 Zymogenous organisms, which included the spore-fonners, were 

 recognised as being scarce in normal soils but becoming very 

 active upon addition of readily fermentable substances. More in- 

 formation in regard to the marine microorganisms is desirable, 

 yet the observation of Jannasch stresses the important point tliat 

 different types of organisms may become selected by diflerent 

 methods of examination and isolation. 



General Approach to Present Study 



To gain a further appreciation of heterotrophic bacterial 

 activity in the sea, more objective qualitative studies on the 

 marine microflora and the types predominating are required. 

 Since the nutritional factor is of basic significance in determining 

 microbial interrelationships, a reconnaissance of the nutritional 

 propensities of the various constituents of bacterial populations 

 of difl^erent marine habitats is particularlv desirable. Although 



