606 Marme Microbiology 



Distribution of Pelagic Chitinoclastic Bacteria 



Free chitinoclastic microbes in pelagic waters seem to be 

 relatively scarce, as was indicated in Figure 4. Of 1,241 colonies 

 on chitin agar plates with pelagic sea water inociila, only four 

 colonies showed evidence of chitin degradation, even after ex- 

 tended incubation. 



Adequacy of Technique 



Unquestionably, optimal culture conditions for pelagic chi- 

 tinoclasts were not discovered in the brief preliminary studies, 

 as is indicated by the greater numbers of colonies that developed 

 on replicate plates of 2216e medium than on chitin-yeast extract- 

 sea water agar. However, the results obtained from zooplankters, 

 in which clearing of chitin in many cases was quite rapid, indicate 

 the medium was capable of detecting chitinoclastic activity. It is 

 entirely possible, however, that materials carried in the inoculum 

 from the zooplankters may have included factors promoting the 

 production of chitinase. 



When first examining culture conditions for marine chitino- 

 clasts, inocula of sea water from the Scripps Institution's pier were 

 used. After a few cruises to pelagic areas it became apparent the 

 types of microorganisms were different, and evaluations of tech- 

 nique were checked with actual pelagic water inocula. In samples 

 from just behind the surf zone, 18.9 per cent of the microbial 

 population was chitinoclastic, while offshore populations were 

 found to contain only 0.32 per cent. In addition, many fungi were 

 encountered in nearshore samples, while they were rarely en- 

 countered away from the influence of land. This increased the 

 difficulty of searching for optimal conditions. Work on shipboard 

 is necessarily more limited in scope than in a laboratory ashore. 



The preliminary culturing experiments indicate chitin, with- 

 out supplementary factors, is not a suitable substrate for esti- 

 mating the pelagic chitinoclastic microflora. The addition of 0.1 

 per cent peptone did not appear to be as suitable as the addition 

 of 0.1 per cent yeast extract to the chitin medium. Further tests 

 using 27 purified isolate of pelagic marine chitinoclasts showed 

 that neither 0.1 per cent chitin, nor 0.1 per cent chitin and 0.1% 

 NH4NO3 in sea water would support growth of these cultures. 



