ALGAL EXCRETION AND BACTERIAL ASSIMILATION IN HOT SPRING ALGAL MATS1

Authors:
Publisher website
Google Scholar
Abstract
SUMMARY: Benthic algal‐bacterial mats are present in the effluents of alkaline hot springs at temperatures between 50 and 73 C. The thin surface layer is composed of the unicellular blue‐green algaSynechococcus lividus. Also present in the surface layer and forming thick, orange mats beneath it, are filamentous, phototrophic, gliding bacteria of the genusChloroflexis, also capable of heterotrophic growth. The very low species diversity and the constancy of the hot spring environment, make these mats a good ecosystem for studying the transfer of nutrients from the algae to the bacteria. To determine whether the alga might supply organic materials to the bacterium, excretion by natural populations ofS. lividuswas studied in the field by means of short‐term radioisotope experiments. Under optimal conditions for photosynthesis, between 3 and 12% of the total14C fixed was excreted as14C‐labeled organic compounds. Variations in cell density at concentrations ofS. lividusapproximating those found in the mat had no effect on the percentage excretion. However, at cell densities below a threshold, level, the percentage excretion increased with diminishing cell density. Except at very low light intensities the percentage of fixed carbon excreted, was very similar for all light intensities tested. Excretion at temperatures approaching the upper limit for growth was not significantly different from the percentage excretion values observed at lower temperatures.14C‐labeled organic compounds excreted during algal photosynthesis could be subsequently assimilated by natural populations of the bacteria present in the mat.

This publication has 28 references indexed in Scilit: