ECOLOGICAL BIOCHEMISTRY - Study Guide - V. M. Isaenko 2005

Chapter 2. ECOLOGICAL AND BIOCHEMICAL INTERACTIONS OF PROKARYOTES, MICROSCOPIC FUNGI, AND ALGAE WITH HIGHER PLANTS AND ANIMALS

2.2. Features of intraspecific and interspecific interactions of microorganisms

Among the diverse ECOLOGICAL AND BIOCHEMICAL interactions of prokaryotes or eukaryotes of the same species, a significant role belongs to those mediated by pheromones (from Greek feros — to bring, produce, direct, and osmos — to drive, desire, induce). However, The Mechanism of bacterial pheromones has its own distinctive features. For example, the pheromones of the bacterium Streptococcus faecalis are represented by several linear Peptides. Each pheromone corresponds to a specific plasmid in Cells that perceive the pheromone as a signal to synthesize a protein promoting conjugation between the pheromone-producing cells and the plasmid-bearing cells. As a result of Cell Fusion, the plasmid-bearing cells transfer copies of their Plasmids to the pheromone-producing cells.

One type of interaction between bacterial cells is mediated by autoregulators that affect Cell Differentiation, sporulation, and the synthesis of BIOLOGICALLY ACTIVE SUBSTANCES (such as zoifem and Antibiotics).

Another type of interaction in prokaryotes is associated with the action of bacteriocins — Proteins that are toxic to other strains of the same species that lack bacteriocins and the plasmids determining their synthesis.

Eukaryotic cells lack identical toxins. Only Yeasts, particularly Kluyveromyces lactis, possess strains that produce a toxin affecting other strains of this family as well as yeasts of other families.

A comparison of intraspecific interactions among Bacteria, Fungi, and Algae indicates the existence of similar effects. At the same time, there are fundamental differences caused by the Chemical Structure of the molecules and their Mechanisms of action. One type of interspecific interaction is inhibition. Both PROKARYOTES AND EUKARYOTES (fungi) produce antibiotics with pronounced antibacterial and antifungal activity.

Antibiotics (from Greek anti — a prefix meaning opposite, and bios — life) are substances of biological origin produced primarily by microorganisms that inhibit the growth of other microorganisms. Plants are capable of producing and releasing allelopathic substances (see Chapter 3) that are similar to antibiotics.

The term phytoncides (from Greek phyton — plant and Latin caedare — to kill) is used to denote inhibitors produced by higher plants that act on microorganisms. Substances secreted by microorganisms that are harmful to plants are called marasmins (from Greek marasmos — decay, exhaustion).

Another type of interspecific interaction is The stimulation of the PRODUCTION OF BIOLOGICALLY active substances by microorganisms when co-cultivated with others that are incapable of producing these same substances. This is characteristic of both prokaryotes (e.g., the binary culture of Streptococcus rimosus and Streptococcus violaceus) and eukaryotes (the fungi Aspergillus rimosus and Aspergillus wentii). Stimulation of The production of biologically active substances is also observed in binary mixtures where one component is a prokaryote and the other is a eukaryote (such as Aspergillus fungi or yeasts).

Bacterial growth can be stimulated by substances produced by other prokaryotes and eukaryotes. For instance, a peptide factor produced by yeasts stimulates the growth of Lactobacillus sanfrancisco. Another example is the growth of the Yeast Candida tropicalis, which is enhanced by biotin produced by Candida mycoderma.

Symbiosis is based on metabolite exchange and occurs in prokaryotes and eukaryotes, as well as between them (e.g., Pseudomonas fluorescens and Volvox aureus).

Thus, a comparison of interspecific interactions between prokaryotes and eukaryotes reveals certain common features, likely due to shared habitats and ecological niches. At the same time, the biochemical mechanisms shaping the ecological characteristics of prokaryotes differ from those of eukaryotes.