Discovery that bacterium is a phosphate gourmet key clue to what makes it most social bacteria

New research into one of the world’s most social bacteria – Myxococcus xanthus, has discovered that it has a gourmet style approach to its consumption of phosphates, which provides a key clue to what makes it the most “social” of bacteria.

Myxococcus xanthus is amazingly social and co-operative for a bacterium. It “hunts” as a pack, it makes a collective decision with other M. xanthus whether to go dormant or not, and it even has methods of policing the behaviour of individual bacteria that try to “cheat” in the collective activity of the group. Now Dr David Whitworth from the Biological Sciences Department of the University of Warwick has also discovered that it appears to seek out and consume phosphate in a “gourmet” manner, providing important evidence as to how such a relatively simple organism is able to act in such a social manner.

Dr Whitworth looked at the signalling pathways used by the bacterium to process information to switch actions on or off. Myxococcus xanthus has an unprecedented number (around 150) of the signalling pathways known as “two component switches” which dramatically increases the level of complexity of information that can be processed by the bacterium. Dr Whitworth focussed on three previously described signalling pathways that were known to be similar to phosphate utilisation pathways (all organisms need to consume phosphate to thrive). Until now most researchers believed that all bacteria only required one phosphate dependent signalling pathway to find the phosphate needed for consumption, and so the other two pathways found in M. xanthus simply did something else. In collaboration with Prof Mitchell Singer of the University of California at Davis, Dr Whitworth found that in fact the bacterium was using all three pathways and part of a further fourth pathway in combination, to detect and utilise phosphates, making it a very sophisticated consumer of phosphates – the bacterial equivalent of a gourmet diner.

That the 3 pathways act in concert probably enables the organism to find phosphates in different chemical states or environmental conditions, or even to exploit the phosphates found in other M. xanthus cells or those of potential prey organisms. Dr Whitworth found that:

• The potential complexity of the information on phosphate levels that the bacterium can process is significantly increased by the findings that there are three phosphate signalling pathways, with considerable interaction between the three pathways.
• A further additional partial pathway also acts as a phosphate level detector – giving the bacterium even more tools to employ as a phosphate gourmet.
• Dr Whitworth also has evidence that the surprising extent of interaction between the three and a half phosphate signalling pathways is also found among the other 140 plus signalling pathways of the bacterium. If three and half pathways are enough to make it a phosphate gourmet, the level of interactions between up to 150 pathways will easily be enough to give Myxococcus xanthus its precocious social skills.