A soil biocontrol agent, biofertiliser and plant growth promoter in one

Dr WJ Botha of the Biosystematics Division attached to the Agricultural Research Council’s Plant Health and Protection Research Institute explains why Streptomyces bacteria are an ideal alternative to chemical fertilisers and growth promoters.

- Dr WJ Botha

FAST FACTS

Streptomyces spp resemble fungi in their morphology, but are actually bacteria.

Most species of Streptomyces are free-living and occur in both natural and agricultural environments.

Streptomyces species function as biocontrol agents or antagonists of soilborne pathogens.

With the expected increase in world population in the coming decades, crop yield per hectare and a reduction in the use of chemicals in agriculture will both be of paramount importance.

Actinobacteria or ‘ray bacteria’ are Gram-positive bacteria that comprise a significant percentage of soil microbial populations, the soil food web and the root microbiome (the community of micro-organisms, such as fungi, bacteria and viruses that exists in a particular environment and colonises the root systems). They resemble fungi in their morphology, forming branching, thread-like filaments, asexual spores in chains and densely packed filaments or mycelia.

Actinobacteria usually grow in warm and damp soil. After a long period of dry weather, their activities slow down. When the soil is moistened, actinobacterial spores ‘awaken’ and release a by-product called geosmin, which causes the characteristic, fresh, earthy smell. Some species form mutualistic relationships with plants, promoting root growth and protection against pathogens. (Mutualism is an interaction between different species that results in beneficial outcomes, promoting reproduction and/or survival of the interacting populations.)

STREPTOMYCES