Introductory Microbiology

Antagonism

• The killing, injury or inhibition of growth of one species of microorganisms by another when one organism adversely affects the environmental of the other. The toxic compounds are antibiotic. An antibiotic is a substance formed by one organism that in low concentrations, inhibits the growth of another organism. Antibiotics is common among Streptomyces isolates, but numerous strains of Micromonospora and Nocardia are also active.
• The most common frequently encountered bacterium synthesize antibiosis are species of Bacillus, strains of Pseudomonas, Species of Penicilium, Trichoderma, Aspgerillus, Fusarium are also excrete antibiotic substance. Antimicrobial compounds against fungi are present in the soil, which inhibit the germination of fungal spores. This phenomenon is termed as fungistasis.
• Cyanide is produced by certain fungi in concentrations toxic to other microorganisms, and algae elaborate fatty acids which exhibit a marked antibacterial activity. Other metabolic products that may result from microbial activity in soil, which are likely to be inhibiting to other species are CH4, sulfides and other volatile S compounds. B. t toxic to lepidopteran insects.
• Myxobacteria (slime (B)) and streptomyces are antagonistic because they secrete potent lytic enzymes which destroy other cells by digesting their cell wall. The degraded cellular material, as well as the released protoplasmic material, serve as nutrients.