Bacteria do compete for the resources among themselves for living. As newer bacteria are produced by reproduction, a variation which leads them to survive better with lesser resources gives them an advantage and this goes with their gene regulation.
Step-by-step explanation:
Law of competitive exclusion was given by Gause which is also known as Gause's law. This law states that when two types of organisms fight for the same limiting resource, they cannot coexist in a ecosystem.
In case of bacteria, their reproduction rate is very high and they reproduce in a geometric progression to achieve a huge number within a very less time. So the nutrients often become a limiting resource within a very small span of time. Now those bacteria with better gene regulation can produce some sorts of protein which can help them exclude others from gathering food, or can help them to gather food more efficiently. This leads to a competitive exclusion of the other species which was incompetent to gather their food.