Chapter 17 - Bacterial Communities in Natural Ecosystems

Abstract

Publisher Summary Complex bacterial communities are found in essentially all natural ecosystems including soils, plants, and surface and ground water, which exhibit great diversity as well as great redundancy in their activity. This chapter describes the microbial communities and diversity in natural systems, functional diversity and resilience of bacterial communities, and importance of microbial communities as source of natural products. The bacterial diversity in normal healthy soil is necessarily very large; however, under stressed or extreme environments, it tends to be much smaller. DNA–DNA hybridization and sequence based techniques such as 16S rRNA sequencing and multilocus sequence typing (MLST) have been used to study the bacterial diversity in natural systems. Estimates of diversity in soil have also been made using DNA reassociation kinetics and cloning and sequencing 16S rRNA genes; however, the diversity estimates were somewhat different. Natural bacterial communities in marine water have lower numbers than their soil counterparts. The redundancy with respect to functional diversity may enable soil microbial communities to be active even when the environmental parameters change constantly. Microorganisms such as actinomycetes and fungi are rich source of a variety of antibiotics. Paclitaxel, an anticancer drug, is produced by many endophytic fungi associated with yew ( Taxus ) species. However, the new cultural and cloning techniques are enhancing the availability of beneficial natural products.