There are limits, and sooner or later all natural populations bump into one or more of them and have to slow down. Charles Darwin once did a simple calculation based on the growth rate of elephants, one of the slowest reproducing animals on the planet. He started with two elephants and worked out that, if nothing stopped them, there would be over 19 million elephants after 750 years of unrestrained population growth. The fact that we are not over run with pachyderms means that something eventually puts the breaks on unrestrained growth.
Bacteria also produce waste products of their metabolism.
These waste products are slightly toxic, and as more and more bacteria produce more and more wastes, the accumulation eventually reaches a level that inhibits the very bacteria that are producing them. Once again, growth must slow down and eventually stop. The lack of food, or the production of waste can both stop a population growing. How much food is left, or how much waste is produced is, in turn, strongly influenced by the number of consumers and producers. The more bacteria we have growing in a bottle, the more food they will be consuming and the more waste they will be producing.