Mi­cro­bial Co­ex­is­tence

Note­wor­thy

Though our daily liv­ing de­pends on the work of oth­ers, near and far, we rarely dis­en­tan­gle the net­work of re­la­tions and in­ter­de­pen­dences that make this pos­si­ble. But just as hu­man so­ci­eties rely on mul­ti­ple ex­ter­nal fac­tors and in­ter­ac­tions, a re­cent study high­lights how the same is true for mi­crobes. 

Re­searchers at Ben Gu­rion Uni­ver­sity of the Negev wanted to un­der­stand how mi­crobes in nat­ural ecosys­tems, where they of­ten make part of com­plex mul­ti­species com­mu­ni­ties, were able to es­tab­lish them­selves and thrive de­spite chang­ing en­vi­ron­men­tal con­di­tions and po­ten­tial an­tag­o­nis­tic neigh­bors. By us­ing a di­verse ar­ray of bac­te­ria and syn­thetic min­i­mal com­mu­ni­ties, they show that mi­crobes can sense one an­other and re­spond in ways that pro­mote sta­bil­ity.  

To ex­am­ine mi­cro­bial re­sponses to fluc­tu­at­ing con­di­tions, the au­thors de­signed an ex­per­i­men­tal setup in which a group of phy­lo­ge­net­i­cally and func­tion­ally di­verse bac­te­ria was sub­jected to dif­fer­ent abi­otic and bi­otic changes in the en­vi­ron­ment. Bac­te­ria were grown in the pres­ence of two con­trast­ing car­bon sources – fruc­tose and a com­plex plant fiber – both in iso­la­tion and in the pres­ence of other mi­cro­bial species. Bac­te­r­ial re­sponses were mon­i­tored by look­ing at pro­teomic pro­files as a mol­e­c­u­lar read­out for meta­bolic ad­just­ments.

Fig­ure show­ing that mi­crobes ac­tively mod­u­late their re­al­ized niches in re­sponse to com­mu­nity com­po­si­tion, re­duc­ing func­tional over­lap as a po­ten­tial mech­a­nism for niche par­ti­tion­ing (mi­cro­bial de­ci­sion-mak­ing), while en­hanc­ing com­mu­nity pro­duc­tiv­ity. Source

These ex­per­i­ments re­vealed that, in fact, bac­te­ria re­spond to the pres­ence of other mi­crobes in their en­vi­ron­ment. In fact, the com­po­si­tion of the com­mu­nity led to con­sis­tent and re­pro­ducible pro­teome ex­pres­sion pat­terns, in­di­cat­ing that the part­ners present, rather than changes in car­bon source, were dri­ving re­sponses. These changes in pro­tein ex­pres­sion also re­vealed a re­duc­tion in func­tional over­lap and an as­so­ci­a­tion with in­creased com­mu­nity pro­duc­tiv­ity, as mea­sured by mi­cro­bial abun­dance. To­gether, the data sug­gest that the pres­ence of spe­cific part­ners trig­gers func­tional ad­just­ments that are im­por­tant for re­duc­ing com­pe­ti­tion and en­hanc­ing the co­ex­is­tence of di­verse species. 

It should not sur­prise us that mi­crobes, with their func­tional ver­sa­til­ity and ca­pac­ity to ef­fi­ciently re­spond to en­vi­ron­men­tal changes, also sense and re­spond to other mi­crobes in their en­vi­ron­ment. A mi­cro­bial neigh­bor be­comes a force be­hind com­mu­nity struc­ture and dy­nam­ics, not just as a com­peti­tor but also as a po­ten­tial part­ner to sta­bi­lize and pro­mote a more peace­ful co­ex­is­tence. 

How to main­tain such a bal­ance might, how­ever, be non-triv­ial.