 predators from within. And by coincidence, these same strains are also better at infecting human cells. Meanwhile, the normally harmless nose bacteria Streptococcus pneumonia becomes infectious when it battles against another species called Haemophilius influenzae. This competitor summons white blood cells to do away with Streptococcus, which can defend itself by producing a thicker coat. But this armour also allows Streptococcus to evade our own immune system, resulting in pneumonia, meningitis and other diseases.
This crossfire effect explains why some bacteria cause potentially fatal diseases, even though they’re not contagious. They go down with their host, because they are not really targeting their host at all. Many human diseases really have nothing to do with us at all. However, some scientists are turning these bacterial wars to our advantage, harnessing the weapons that they use against one another.