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The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.Aspergillus niger is a fungus produces citric acid.Trichoderma species are free-living fungus that is very common in the root ecosystems. It is effective biocontrol agents of several plant pathogens.In paddy fields, cyanobacteria serve as an important biofertilizers.