Microbiologia

Microbial Diversity: Exploring the Unexplored
Manisha Kapur and Rakesh Kumar Jain*
Institute of Microbial Technology, Sector 39-A, Chandigarh-160036, India
* Corresponding author Phone: +91-172-2690713/2695215, Ext 542, Fax: +91-172-2690585/2690632 E-mail: rkj@imtech.res.in

Introduction
The most useful definition of biodiversity is that given by the International Union for Conservation ofNature and Natural Resources; biodiversity encompasses all life forms, ecosystems and ecological processes and acknowledges the hierarchy at genetic, taxon and ecosystem levels. Microbial diversity on the other hand includes the diversity of bacteria, protozoans, fungi, unicellular algae and constitutes the most extraordinary reservoir of life in the biosphere, and one which we have only begun toexplore. Diversity is composed of two elements: richness and evenness, so that the highest diversity occurs in communities with many different species present (richness) in relatively equal abundance (evenness) (Huston, 1994). The richness and evenness of bacterial communities reflect selective pressures that shape diversity within communities. Measuring these parameters is most useful whenassessing treatment effects (e.g., physical disturbances, pollution, nutrient addition, predation, climate change, etc.) on community diversity. For much of the last century, microbiologists have been aware that we know the nature and identity of only a tiny fraction of the inhabitants of the microscopic landscape. While most people are very familiar with the diversity of life in the plant and animalkingdoms, few actually realize the vast amounts of variability present in the bacterial populations. Microorganisms represent the richest repertoire of molecular and chemical diversity in nature as they

underlie basic ecosystem processes. The current inventory of the world’s biodiversity is very incomplete and that of viruses, microorganisms and invertebrates is especially deficient. Scientistshave identified about 1.7 million living species on our planet. Studies indicate that the 5,000 identified species of prokaryotes represent only 1 to 10% of all bacterial species, therefore we have only a small idea of our true microbial diversity (Stanley, 2002).

Culture Dependent Vs Culture Independent Methods
The detailed analysis of microbial diversity within an environment can be dividedinto two broad categories: culture dependent studies and culture independent studies (Juck et al., 2000). In culture dependent methods, bacteria are isolated from environmental samples with culture medium. Nucleic acid is then extracted from the bacterial culture. The biggest drawback in exploring bacterial biodiversity is the issue of viable but non-cultivable organisms. Diversities in bacterialcommunities are normally determined by phenotypic characterization of isolated strains. A problem is that phenotypic methods can be used only on bacteria which can be isolated and cultured. While many advances have been made in microbiological culture techniques, it is still not possible to grow a majority of bacterial species using the standard laboratory culturing techniques. Conventionalcharacterization of microbial strains therefore has been subjected to debate, as it is dependent on the ability of the strains to grow under specific environmental conditions (Bakonyi et al., 2003). These types of classic

microbiological methods are indirect and produce artificial changes in the microbial community structure. So, most bacteria will be excluded when phenotypic diversity is estimated.The isolated bacteria may account for only a minor proportion of the total bacterial diversity in soil, while our knowledge about the dominant part is very scant. This has led to the current uncertainty regarding the true extent of bacterial life, and, due to the medicinal and industrial properties of known bacteria, has led many to hypothesize that uncultured species have many positive...