ZoBell — 116 — Marine Microbiology 



Upham (1944) who have prepared a Hst of marine bacteria and have 

 described 60 new species. Of these, 49 are flagellated, 45 are Gram- 

 negative, and 54 are rod-shaped. The average cell is 2 to 3 /z in length 

 by 0.4 to 0.6 fx in width. 



Cultural characteristics : — In general, marine bacteria grow more 

 slowly and the colonies are smaller than most microorganisms from soil, 

 sewage, and milk. Whereas plates inoculated with terrestrial bacteria 

 may be counted with good results after incubation from two to seven days 

 at optimal temperatures, the numbers of macroscopically visible colonies 

 of marine bacteria are still increasing significantly after ten days' incu- 

 bation (see Table IX on page 45). Diffuse, spreading colonies are en- 

 countered less frequently on plates inoculated with marine materials than 

 on plates inoculated with soil or fresh water. 



Depressed colonies occur on nearly all agar plates inoculated with sea 

 water or marine mud, and occasionally an appreciable portion of the 

 medium will be liquefied by agar digesters. Agar digesters are also found 

 in fresh water and soil, but not nearly as frequently as in the sea. Because 

 they are so conspicuous on agar plates, one may get the impression that 

 agar digesters constitute a sizeable percentage of the marine microflora, 

 but actually an average of only about one to two per cent of the colonies 

 prove to be agar digesters. Over ten per cent of the pure cultures of 

 marine bacteria described in the literature digest agar, but this is because 

 agar digesters have been selected for special studies. 



Typical of water bacteria, more than half of those occurring in the 

 sea are chromogenic. An examination by ZoBell and Feltham (1934) of 

 several thousand colonies developing on nutrient agar inoculated with 

 sea water or marine mud showed that 69.4 per cent of them produced pig- 

 ments. The distribution of colors was as follows: 31.3 per cent yellow, 

 15.2 per cent orange, 9.9 per cent brownish, 7.4 per cent fluorescent, 5.4 

 per cent red or pink, and 0.2 per cent green. The commonest type of 

 fluorescence exhibited is greenish. Indigo, black, and silvery-sheen col- 

 onies have been observed on special media. Twenty species of yellow 

 chromogens were described by ZoBell and Upham (1944), including 

 Flavohaclerium marinotypicum, FL marinovirosum, Fl. okeanokoites , Pseu- 

 domonas neritica, Ps. obscura, Ps. oceanica, Ps. vadosa, Ps. xanthochrus, 

 Vibrio adaptatus, V. marinoflavus , and V. marinovulgaris. 



In order to accentuate pigment production, the bacteria were grown 

 in sea-water media enriched with Bacto-tryptone, neopeptone, and beef 

 extract. The plates were incubated at 4° C. for three weeks following a 

 preliminary incubation of 4 days at 25° C. Lower temperatures tend to 

 favor pigment production. The unpublished observations of Harvey 

 Upham working in the Scripps Institution laboratories indicate that in- 

 fusions of fish, octopus, mussel, and other tissues promote the production 

 of pigments by marine bacteria. Many marine bacteria gradually fail to 

 produce pigment during prolonged laboratory cultivations. 



Yellow colonies predominated among those observed by Gee (19326) 

 in sea water and mud around the Florida Keys. Of 855 colonies examined, 

 593 were yellow and 135 were red. According to Peirce (1914), the red 

 color of brine around marine salterns may be due to the abundant growth 

 of chromogenic bacteria, although other organisms including Protococcus 

 salinus and Dimaliella salina may be partly responsible. The discolora- 

 tion of halibut has been shown by Bedford (1933^^) to be due to the 



