ZoBell — 118 — Marine Microbiology 



bacteria studied by ZoBell and Grant (1943) converted 30 to 35 per cent 

 of the glucose into bacterial protoplasm or intermediate products of me- 

 tabolism, the rest being oxidized to carbon dioxide and water as a source 

 of energy. Waksman and Carey (19356) reported that around 60 

 per cent of the organic matter assimilated by marine bacteria is oxidized 

 and 40 per cent is converted into bacterial protoplasm or intermediate 

 products. It will be interesting to ascertain whether this economy of 

 utilization is peculiar to marine bacteria which have become adapted to 

 living in the extremely dilute organic nutrient concentrations existing 

 in the sea. 



Rarely in the open ocean are bacteria encountered which produce acid 

 from lactose. Gas producers are found only in contaminated water. Lac- 

 tose fermenters are common in soil and most fresh-water bodies. Their 

 sanitary significance is discussed in Chapter XVI. Very few marine bac- 

 teria produce acid from sucrose, maltose, xylose, glycerol, mannite, or 

 salicin, and gas producers have not been reported from the high seas. 

 However, like glucose and lactose, most of these carbon compounds can be 

 assimilated by marine bacteria. About one-third of the described species 

 of marine bacteria metabolize starch, but little, if any, acid and no gas is 

 produced from starch. The weak fermentative power of marine bacteria 

 has been mentioned by Coupin (191 5). 



As a group, marine bacteria are actively proteolytic, rapidly attacking 

 most kinds of proteinaceous materials. Nearly all of them liberate am- 

 monia from peptone, and approximately three-fourths of them liquefy 

 gelatin. So many marine bacteria liquefy gelatin that it is not a satis- 

 factory solidifying agent for plate-count media. Only a few marine bac- 

 teria liberate detectable quantities of indol from tryptophane. Among 

 the sixty new species described by ZoBell and Upham (1944), only Vibrio 

 adaptatus and Vibrio marinofulvus formed indol in tryptophane broth. 



The observations of Gran (1902), Drew (1912), Kellerman and 

 Smith (1914), Molisch (1925), and others on the abundance of denitri- 

 fiers in the sea has focussed attention upon this group of bacteria. Some 

 workers have concluded that most marine bacteria require nitrate, and 

 that many reduce nitrate to nitrogen. The media employed by Berkeley 

 (1919), LiPMAN (1926), Bavendamm (1931), Gee (19326), and other ma- 

 rine microbiologists all contain nitrate. However, ZoBell (1941a) failed 

 to find that nitrate enhanced the growth of marine bacteria. A good many 

 marine bacteria reduce nitrate to nitrite in appropriate media and a few 

 liberate nitrogen from nitrate, but marine bacteria are not distinctive in 

 this respect. 



Luminescence is not necessarily a physiological property of marine 

 bacteria, although most described species of photogenic bacteria have 

 been isolated from marine materials. When provisions are made for their 

 detection, photogenic bacteria are found in most samples of sea water, 

 and they are often associated with certain marine animals in considerable 

 abundance. 



Several species of photogenic bacteria, some of which may prove to be 

 identical, have been isolated from the sea and described. Besides the nine 

 species of Fischer (1894a) listed on page 3-4, Fischer (1886) described 

 Photobacterium indicum and Ph. phosphorescens (Fischer, 1887). Beije- 

 rinck (1889) described Ph. luminosum for the first time and gave addi- 

 tional information on Ph. phosphorescens, Ph. indicum, and Ph. fischeri. 

 The latter organism has been described by Johnson and Shunk (1936) 



