Abundance and Diversity of Microorganisms in Soils and Associated Substrates (Leaf Litter and “Suspended Soil”) in Some Nature Reserves of Vietnam

Abstract

A comprehensive study has been carried out, and a quantitative and qualitative characteristic of the soil prokaryotic community of zonal Ferralsol and intrazonal Fluvisol of Vietnam, as well as associated leaf litter and “suspended” soil from epiphytic ferns, has been given. The greatest number of bacteria, determined by the direct luminescence method, was associated with samples of Fluvisol, while the lengths of fungal and actinomycete mycelium were the largest in mountainous ferralitic soils. Bacteria of the genus Streptomyces, included in the saprotrophic bacterial complex of the studied substrates, make a significant contribution to the destruction of plant material. The bacteria of the phyla Firmicutes (80%) and Proteobacteria (15%) predominated in the prokaryotic community of the zonal red-yellow humus-ferrallitic soil, while the phyla Proteobacteria (51%) and Actinobacteria (38%) dominated in the sample of the “suspended” soil. The phyla Chloroflexi, Acidobacteria, Bacteroidetes, and Cyanobacteria were significantly less represented. With significant differences at the level of genera in the studied substrates, similar functional groups of microorganisms were identified: xenobiotic decomposers, nitrogen cycle bacteria, extremophiles, as well as bacteria that inhibit the growth of micromycetes. The metabolically active part of the prokaryotic community, represented by the phyla Proteobacteria, Actinobacteria, and Acidobacteria, was the highest in the “suspended” soil and the least active in the litter and horizon A of Ferralsol, which correlated with the high abundance of these phyla and the significant taxonomic diversity of bacteria in this locus. Functional genes (nifH and alkB) were detected in all studied substrates. The number of copies of functional genes was the highest in the “suspended” soil sample, which makes this locus promising for isolating strains with high biotechnological potential.