The phrase "new bacterium" means a recently discovered type of tiny living organism that exists all around us, which has never been seen or identified before. Full definition
It's the death and inevitable breakdown of these cells that make your body look cozy to a whole host of new bacteria. (washingtonpost.com)
Any new animal, especially one imported from another country, could introduce new bacteria into a pet owner's household. (sciencedaily.com)
After cooking, meats are free of bacteria, but leaving them warm for an extended time will invite new bacteria to settle in and start growing. (meatsandsausages.com)