Abstract

Degradation of organic wastes and recycling of nutrients enhanced by various microbes of both bacterial and fungal species available at the entrance, twilight and dark zones of four different caves such as Pannian, Samanar, Ushman and KKB caves at Madurai was investigated. The roles of chemoheterotrophic and chemoautotrophic bacteria were found to be essential in cave ecosystem. The most important chemoheterotrophs were ammonifiers such as Bacillus sp., Clostridium sp., Serratia sp. and Pseudomonas sp. Whereas Nitrite bacteria like Nitrosomonas sp., Nitrosococcus sp. and Nitrobacter winogradskyi,Nitrococcus mobilis derived energy from the oxidation of ammonia and nitrite respectively. Many heterotrophs thrive on the organic releases from nitrifying bacteria. Such heterotrophs involved in the nitrogen cycle were nitrate-reducing bacteria while denitrifiers were sparse in comparison to nitrate reducers due to absence of an anaerobic atmosphere. A total of 15 mesophilous and four thermophilous fungi were isolated from the cave soil samples. Among 15 mesophilous fungi, 11 species belong to Deuteromycetes, 3 species are zygomycetes and 1 species belongs to Ascomycetes. The number of species and CFU of thermophilous fungi also decreased towards dark zone. Serratia sp. and Bacillus sp. were isolated from all the samples at the E, T and D zones of the studied caves. These two bacterial colonies were subjected to quantify enzymes such as cellulose and amylase respectively. The production of cellulose by Serratia sp. at 35°C, pH 6.5 and in substrate glucose is considerably more. The production of amylase by Bacillus sp. seem to be more at 35°C and the substrate ammonium nitrate is considerably ideal for the synthesis of higher quantity of amylase by Bacillus sp. In all the caves, D zone samples had more cellulase and amylase enzymes than the E and T zone samples. Apart from cellulase and amylase, the presence of lipase, catalase and RuBisCo also were identified from the study caves. The nutrient NO₃was found to be more in all the samples. In the caves, nitrogen (N) compound was more than P and K. The FT-IR spectrum results showed that stretching of mineralized compounds were more at the D zone samples compared with E and T zone samples, due to microbial role at D zone with the aid of their enzymes which eventually degrade the complex organic matter into simpler forms.

Key words: Ammonifiers, RuBisCo, anaerobic, lipase, catalase.