Truce with oxygen - A naerobiosis outcompete aerobiosis in the Antarctic lacustrine bacteria

Abstract

The total number of bacteria counted directly by epifluorescent microscopy showed that they ranged from 10 sup(8)-10 sup(-1) in Antarctic lake water samples. The percentages of retrievable viable counts (RVC) of anaerobic bacteria (AnB) was greater than aerobic counts. Among the different groups of anaerobes, the order of retrieval was Thiobacillus denitrificans like organisms (TDLO) greater than fermentative bacteria (FB) greater than sulfate reducing bacteria (SRB). The total direct anaerobic viable counts (TDAnVC) was one order more than the total direct aerobic viable counts (TDAeVC). Laboratory experiments with one of the lake-isolates indicated that there was a tendency to express higher viability of 61% at redox potential (Eh) ranging from -281 to -335 mv. It is suggested that the disposition to express increased viability under reducing conditions is a strategy to counteract stress due to supersaturation of oxygen in the cold lacustrine environment.