Salmonella gets its host to arm its secret weapon | Not Exactly Rocket Science

[![Salmonella][1]][2]Bacteria wield all sorts of molecular weapons that allow them to infiltrate their hosts. But one microbe – _Salmonella enterica – _has a particularly devious trick. It uses weapons that arm _themselves_ by manipulating the host’s own proteins. When this bacterium infects cells, it turns them into accomplices to their own downfall.

_S.enterica _causes a variety of different illnesses including food poisoning and typhoid fever. There are over 2,500 different varieties and Chittur Srikanth from Harvard Medical School has been studying one called Typhimurium, which infects mice. In the first moments of infection, Typhimurium_ _injects a small arsenal of proteins into its victim, which subvert its structure, defences and communications.

One of these injected weapons is known appropriately enough as SipA, or Salmonella invasion protein A. It has two business ends, both of which pose a threat to a host cell. One of them causes a host protein called actin to clump together into long filaments. These act as guide ropes that help to draw _Salmonella_ into the cell. The other end of SipA causes white blood cells to enter the lining of the intestines, leading to inflammation and diarrhoea – a symptom that allows _Salmonella_ to spread from one individual to another.



This is an essential event. When Srikanth engineered a version of SipA without the amino acids that normally attract caspase-3, the protein couldn’t be cleaved in two. As a result, _Salmonella_’s invasion was cut short. Infected mice showed no signs of inflamed bowels or symptoms of food poisoning.


This trick isn’t limited to SipA. Other proteins that are injected by _Salmonella_, and those from other gut bacteria like _Escherichia coli _and _Shigella flexneri_, also carry targets for caspase-3. And the majority of these proteins, like SipA, have two functions, with different ends performing different jobs.


**Reference: **Science [][3]

**More on infectious bacteria: **

* [Why gonorrhoea is like a general sabotaging his own siege][4] * [Disease by coincidence – why we’re caught in the crossfire of a hidden war][5] * [When bacteria fight bacteria, we lose][6] * [MRSA in pigs and pig farmers][7] * [Super-bacteria eat antibiotics for breakfast][8]


[1]: (Salmonella) [2]: [3]: [4]: (Permanent Link: Why gonorrhoea is like a general sabotaging his own siege) [5]: (Permanent Link: Disease by coincidence – why we’re caught in the crossfire of a hidden war) [6]: (Permanent Link: When bacteria fight bacteria, we lose) [7]: (Permanent Link: MRSA in pigs and pig farmers) [8]: (Permanent Link: Super-bacteria eat antibiotics for breakfast) [9]:


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