ENVIRONMENTAL MICROBIOLOGY - M. I. Chernyavskaya - 2016

Introduction

Microorganisms are ubiquitous. For example, a single gram of soil contains billions of them. Organized into taxonomic groups, they exhibit diverse properties and interact with one another in various ways. Environmental microbiology is the science that explores The Diversity of microorganisms within Earth's biomes, while also developing approaches to investigate and subsequently harness their metabolic activity.

The terms "Microbial Ecology" and "environmental microbiology" only came into widespread use in the 1960s, although ecologically oriented studies of microorganisms had begun long before that. As early as the 17th century, A. Leeuwenhoek (1632–1723) observed microorganisms in droplets of rainwater (their natural habitat) and investigated the effects of pepper (an environmental factor) on them.

S. N. Winogradsky (1856–1953) and M. W. Beijerinck (1851–1931) are widely regarded as the founding fathers of environmental microbiology, having established the principles for obtaining enrichment cultures. Winogradsky was the first to utilize gradients of light, sulfide, and oxygen to study natural populations of sulfide-oxidizing photoautotrophic Bacteria, sulfate-reducing bacteria, and chemoautotrophic sulfide- and sulfur-oxidizing bacteria that coexist in a single habitat and carry out interdependent processes. The model system he created became known as the "Winogradsky Column.">

Currently, several primary Research Areas in environmental microbiology can be distinguished:

1) autoecology;

2) demecology (population ecology);

3) synecology;

4) ecophysiology;

5) ecobiotechnology.

Autoecology (from the Greek autos — self) — the branch of ecology that studies the effects of external abiotic factors (Physical and Chemical) on microorganisms.

Determining The properties of a group of individuals belonging to the same species (a population) is the subject of demecology. It is well established that populations possess characteristics that cannot be defined for an individual Organism alone, such as population size, growth rate of Abundance, and mean body size. Because the population is the primary focus of demecology, it is also referred to as population ecology.

Synecology (from the Greek syn — together) — the branch of ecology that examines the interactions between a given microorganism and surrounding organisms, i.e., biotic factors. Thus, the subject of synecology is biological communities, and its focus is the diversity of interspecific relationships within those communities. Microglial relationships can manifest as:

1) Symbiosis:

✵ true symbiosis — two or more species create mutually beneficial conditions for each other's growth;

✵ metabiosis — only one partner derives benefit. Of particular interest is the syntrophic type of cooperation, in which the interaction of different microorganisms enables a process that neither of them could accomplish independently. For instance, bacteria of the genus Arthrobacter, in association with certain Streptomyces species, can completely degrade the organophosphorus insecticide diazinon, utilizing it as a carbon and energy source, whereas neither organism can grow on this substrate on its own;

✵ satellitism — a form of metabiosis where the growth of one microorganism is stimulated by another through the secretion of growth factors;

✵ synergism — members of an association stimulate each other's growth by releasing metabolic byproducts;

2) antibiosis (competitive relationships):

✵ antagonism — active competition between species resulting in the inhibition or complete suppression of one microorganism by another, or mutual suppression;

✵ predation — one group of organisms consumes another as a food source;

✵ parasitism — one species (the parasite) utilizes another species (the host) as a source of nutrients and habitat, causing harm to the host in the process.

The interactions between microorganisms and macroorganisms in the broader sense are classified as symbiosis and may take the form of:

✵ mutualism — mutually beneficial symbiosis, such as the association between marine animals (fish, Mollusks) and luminescent bacteria (Photobacterium, Vibrio) that produce chitinase, an enzyme essential for hydrolyzing the shells of plankton, which serve as the primary food source for most relatively large marine animals;

✵ parasitism — one of the symbiosis partners, in this case the macroorganism, suffers adverse effects from the other partner, the microorganism, which acts as a pathogen. Parasitism is quite widespread among microorganisms. The impact of parasites on the macroorganism's state stems not only from trophic interactions (using the host organism as a habitat and nutrient source) but also from pathogenic effects driven by the toxic and immunologically foreign metabolites of the parasites;

✵ commensalism — microorganisms feed at the expense of the host macroorganism without causing it any harm. This type of interaction can be observed, for instance, in the plant rhizosphere. During the GROWTH AND DEVELOPMENT of a plant, so-called ROOT deposits form in the soil, consisting of root exudates (low-molecular-weight compounds such as sugars, Hormones, Vitamins, Amino Acids, etc., released by plant roots into the soil), high-polymer polysaccharide and proteinaceous mucilage, and sloughed-off root Cells. Many microorganisms utilize root deposits as a nutrient source, which is why a higher microbial density—the rhizosphere effect—is observed around plant roots.

An important branch of environmental microbiology is ecophysiology, which studies microorganisms in relation to the ecological niche they occupy—the set of conditions ensuring the species' existence. METABOLISM/2.html">THE CONCEPT OF an "ecological niche" encompasses not only the physical space inhabited by a specific organism, but also environmental conditions, its trophic position, and its functional role within the community. In microbiology, the ecological (fundamental) niche corresponds most closely to a physiological group of organisms, i.e., a group sharing specific functional properties (e.g., nitrogen fixers, sulfate reducers, methanogens, etc.). Ecological niches can be narrow or broad. However, two organisms with identical requirements undergoing competitive interaction cannot occupy the exact same ecological niche (Gause's law); consequently, the realized ecological niche is always narrower than the potential one.

Developing approaches to utilize microorganisms for solving environmental problems is a key focus area of Environmental Biotechnology. Microorganisms are particularly active in treating natural and industrial environments contaminated with various pollutants, such as crude oil, petroleum products, pesticides, industrial waste, and more.