Response of aquatic bacterial populations to substrate enrichment

Abstract

The responses of natural bacterial populations in the waters of the Kiel Fjord, Germany, and in Lake Kinneret, Israel, to additions of organic substrates were followed. Generally, upon substrate addition, relatively higher incorporation of radiotracers was noted in the preincubated samples. Growth responses to substrate addition even in starved populations was only significant after 24 h. Incorporation rates of 3H-thymidine and 3H-leucine were more sensitive indicators of bacterial response to substrate additions than cell counts. Continued cell replication in unsupplemented controls, and insignificant increase over time of radiotracer incorporation in most of the fresh samples with added supplements, indicated that the indigenous bacterial populations in Kiel Fjord and Kinneret were apparently not substrate limited. -Authors