Characterization of anaerobic heterotrophic bacteria isolated from freshwater lake sediments

Abstract

Strict anaerobic culture techniques were used to quantitatively and qualitatively evaluate the anaerobic heterotrophic bacteria present at the sedimentwater interface of hypereutrophic Wintergreen Lake (Augusta, Mich.). Anaerobic plate counts remained constant from March through December, 1973, ranging from 2.4 x 106 to 5.7 x 106 organisms/g (dry weight) of sediment. The isolatable bacteria represented a small percentage of the total microbial community, which was shown by direct microscopic counts to be 2.0 x 1011 organisms/g (dry weight) of sediment during June and July. Bacteria of the genus Clostridium dominated the isolates obtained, accounting for 71.8% of the 960 isolates examined. A single species, Clostridium bifermentens, comprised 47.7% of the total. Additional bacterial groups and the percentage in which they were isolated included: Streptococcus sp. (10.8%), unidentified curved rods (9.5%), gram-positive nonsporing rods (5.6%), and motile gram-negative rods (1.9%). Temperature growth studies demonstrated the ability of all the isolates to grow at in situ sediment temperatures. Gas-liquid radiochromatography was used to determine the soluble metabolic end products produced from [U-14C]glucose and a U-14C-labeled amino acid mixture by representative sedimentary clostridial isolates and by natural sediment microbial communities. At in situ temperatures the natural sediment microflora produced soluble fermentative end products characteristic of those elaborated by the clostridial isolates tested. These results are considered strong presumptive evidence that clostridia are actively metabolizing in the sediments of Wintergreen Lake.

Irrigation Water as a Potential Preharvest Source of Bacterial Contamination of Vegetables

“…The level of anaerobic spore formers observed in our water samples was however lower than has been reported by Molongoski and Klug (1976). Molongoski and Klug (1976) recovered up to 6 log of anaerobic spore formers from fresh water lakes. Although low aerobic spore formers level was observed in the water samples, it may not be suitable for irrigation of fresh produce because of the possibility of microbial growth and cell division after attachment and infiltration on the vegetables.…”

Anaerobic metabolism of particulate organic matter in the sediments of a hypereutrophic lake*

“…I), ihe high protein content of the organic matter reaching the sediments (Molongoski & Klug. 1980) and the predominantly proteolytic nature of the anaerobic heterotrophic bacteria isolated from pelagic sediments in Wintergreen Lake (Molongoski & Klug, 1976) all indicate ihat the high ammonia concentratit>ns detected in the sediments (Fig. 7) and overlying water (Fig.…”

“…The percentage of hydrogen sulphide produced in pelagic sediments in Wintergreen Lake by dissimilatory sulphate reduction as compared to the decomposition of organic sulphurcontaining compounds (putrefaction) was not determined. The putrefactive nature of the anaerobic heterotrophic sediment microflora (Molongoski & Klug, 1976), as well as the absence of sulphate in the interstitial water (except at autumn turnover and during occasional periods during the summer when turbulence briefly introduced sulphate to the sediment-water interface; Fig. 7), suggested that putrefaction may be a more important source of hydrogen sulphide than sulphate reduction in these sediments.…”

Quantification and characterization of sedimenting particulate organic matter in a shallow hypereutrophic lake*

“…The high protein content of the seston may have derived from the large populations of blue-green algae, particularly v4nflfcae«a and Microcystis. which annually dominate the phytoplankton of the lake (Manny, 1971;Molongoski & Klug. 1976), The latter organisms, on an average dry weight basis, may consist of greater than 50% protein {Fogget ai.…”