The main habitat of endospore forming Bacillus organisms is the soil. Likewise, Bacillus subtilis is most commonly found in soil environments and on plant undergrowth. These mesophilic microbes have historically been considered strict aerobes. Thus they are likely to be found in O and A surface horizon s where the concentration of oxygen is most abundant and temperatures are relatively mild.
Consider how this organism functions in a competitive microbial community: when carbon, nitrogen, and phosphorous nutrient levels fall below the bacterium’s optimal threshold, it produces spores. Antibiotic production increases B. Subtilis chance at survival as the organism produces spores and a toxin that might kill surrounding gram positive microbes that compete for the same nutrients. These microbes form spores in times of nutrient exhaustion. When the nutrients required for the bacteria to grow are abundant, they exhibit metabolic activity. These organisms can produce antibiotics during sporulation. Examples of antibiotics that Bacillus subtilis can produce include polymyxin, difficidin, subtilin, and mycobacillin. Many of the Bacillus microbes can degrade polymers such as protein, starch, and pectin, therefore; they are thought to be important contributor to the carbon and nitrogen cycles. When they cause contamination, they may result in decomposition. Actually, quite a few of the Bacillus organisms are primarily responsible for the spoilage of food.