Competitive exclusion of pathogenic microbes by beneficial bacteria

In nature, bacteria compete for carbon sources (energy), macronutrients, and micronutrients. As a part of this competition various microbes engage in their own form of chemical warfare by making antimicrobial compounds that work against competing microbes. We are most familiar with these compounds as many of our common antibiotics including polymyxin and bacitracin come from common soil spore forming microbes.

In addition to manufacturing antibiotic pharmaceuticals (which are highly refined compounds), the natural production of antimicrobial compounds is a key part of the science of using microbes to competitively exclude pathogenic and opportunistic pathogenic microbes.

Examples of applications using microbial competitive exclusion:

1. Reducing pathogenic Vibrio sp in shrimp aquaculture
2. Lower Salmonella in poultry houses
3. Reduce fungal wilts (root fungal pathogens) in agriculture
4. Help reduce pathogens on floors in food processing facilities
5. Lower E coli and other enteric microbes in wastewater
6. Help control filamentous bulking in wastewater
   

In all cases the introduced beneficial microbes grow well in the target environments. As a part of this growth, the microbes manufacture desirable metabolites that inhibit or prevent the growth of the problematic pathogenic microbes. I have been working at Aster Bio of identifying numerous microbes with the ability to exclude competing pathogenic organisms. It is interesting in application to see how a single microbe such as Bacillus subtilis can help prevent overgrowth (note overgrowth rather than totally prevent) of pathogenic fungi, cyanobacteria, and gram negative bacteria. As major companies continue to focus of probiotics and microbial controls, we will see greater acceptance of competitive exclusion as a means of pathogen control rather than relying on more broad spectrum antimicrobials.

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