Abstract
A wide range of prokaryotes produce and excrete bacteriocins (proteins with antimicrobial activity) to reduce competition from closely related strains. Application of bacteriocins is of great importance in food industries, while little research has been focused on the agricultural potential of bacteriocins. A number of bacteriocin producing bacteria are members of the phytomicrobiome, and some strains are plant growth promoting rhizobacteria (PGPR). Thuricin 17 is a single small peptide with a molecular weight of 3.162 kDa, a subclass IId bacteriocin produced by Bacillus thuringiensis NEB17, isolated from soybean nodules. It is either cidal or static to a wide range of prokaryotes. In this way, it removes key competition from the niche space of the producer organism. B. thuringiensis NEB17 was isolated from soybean root nodules, and thus is a member of the phytomicrobiome. Interestingly, thuricin 17 is not active against a wide range of rhizobial strains involved in symbiotic nitrogen fixation with legumes or against other PGPR. In addition, it stimulates plant growth, particularly in the presence of abiotic stresses. The stresses it assists with include key ones associated with climate change (drought, high temperature, and soil salinity). Hence, in the presence of stress, it increases the size of the overall niche space, within plant roots, for B. thuringiensis NEB17. Through its anti-microbial activity, it could also enhance plant growth via control of specific plant pathogens. None of the isolated bacteriocins have been examined as broadly as thuricin 17 on plant growth promotion. Thus, this review focuses on the effect of thuricin 17 as a microbe to plant signal that assists crop plants in managing stress and making agricultural systems more climate change resilient.
Highlights
Microbes produce antimicrobial substances to compete with each other for nutritional resources and niche space
Bacteriocins of Gram-positive bacteria are more discussed in more detail as our target bacteriocin, thuricin 17 is produced by a Gram-positive bacterium
Bacteriocin production by Bacillus plant growth promoting rhizobacteria (PGPR) is poorly understood and none have been studied for plant growth promotion as extensively as thuricin 17, discovered in our laboratory (Smith et al, 2008) and produced by B. thuringiensis NEB17 (BtNEB17), a non-symbiotic endophytic bacterium isolated from soybean root nodules
Summary
Microbes produce antimicrobial substances to compete with each other for nutritional resources and niche space These excreted microbial substances comprise a range of types: broad-spectrum non-ribosomal antibiotics, metabolic products (organic acids), lytic agents (lysozymes), and bacteriocins (Riley, 1998). Thuricin 17 a Phyto-Biostimulant Bacteriocin by bacteria (Arnison et al, 2013). They are distinct for antibiotics in that they inhibit organisms closely related to the producer strains, active at very low concentrations and are formed in the ribosome (Mak, 2018). Most research around bacteriocins has been conducted on lactic acid bacteria (LAB), known for their biopreservative potential in the food industry, and often produced by “generally recognized as safe” (GRAS) microbial strains (O’sullivan et al, 2002). Since classification of bacteriocins is based on structure, bacteriocins belonging to the same class have similar modes of action (Iwatani et al, 2011)
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