But with bacterial attack, the BBC reports that we should be equipped to fight back against some of the most lethal strains,
- The gut infection Clostridium difficile can be defeated by a cocktail of rival good bacteria, experiments in mice show.
When C. difficile bacteria overwhelm the gut, it can be fatal and difficult to treat with antibiotics.
A UK team showed a combination of six bacteria could clear the infection.
The study, published in PLoS Pathogens, builds on faecal transplant procedures - which are used to introduce competing bacteria.
C. difficile bacteria live in many people's guts alongside hundreds of other species - all fighting for space and food.