Chapter 47 



The Differentiation of Certain Genera 

 of Gram Negative Bacteria Frequently 

 Encountered in Marine Environments'^'' 



J. M. Shewan 



Xo most of us with any experience in marine microbiology, the 

 classification of our isolates has always been a problem. Some of 

 you no doubt may consider classification or taxonomy a some- 

 what sterile field of enquiry. It is more important, you may say, 

 to know what the micro-organisms do in tlie marine environment 

 rather than to know what they are or to give them a name. A 

 number would do just as well. Precise identification may, how- 

 ever, be of more than academic interest. For many practical prob- 

 lems it is becoming increasingly evident that we must be able to 

 identify our organisms if any headway is to be made, and in 

 particular, if we are to be able to compare our data with those 

 of other workers. For example, in our work on fish spoilage, we 

 know that fish from the same area but caught at different seasons, 

 spoil at different rates, as do fish caught at the same time of 

 year but from different fishing grounds. It seems almost certain 

 that these differences are due to differences in the microbial flora, 

 but unless we have the means of analysing the flora present on 

 the fish, quickly and reasonably accuratelv, at least to the generic 

 level, - indeed we think it must often go to the species level - we 

 cannot disentangle the importance of the bacterial flora from 

 other factors, such as the physical condition or chemical com- 

 position of the fish. Or to take another example. One of the most 

 important features of Professor Kriss's recent book on Marine 

 Microbiology (38) has been tlie demonstration of the usefulness 

 of marine bacteria as indicators of ocean currents. It is clear, 



* The work described in this paper was carried out as part of the programme of 

 the Department of Scientific and Industrial Research. (Crown Copyright Re- 

 served ) 



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