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Mikrobi sodelujejo med seboj pri koriščenju hranil iz okolja, premikanju, virulenci, privzemanju železa, medsebojni zaščiti, itd. Za evolucijsko uspešnost medsebojnega sodelovanja je pomembna sposobnost prepoznavanja sorodnih (`kin`) in / ali ločevanja manj sorodnih organizmov ('nonkin'). V okviru magistrske naloge smo proučevali sorodstvene interakcije med sevi bakterije Bacillus subtilis pri rojenju po poltrdnem agarskem gojišču. Če dva bakterijska seva nista sorodna/kompatibilna med seboj, pride do antagonističnih interakcij in tekmovanja za kolonizacijo površine. V nalogi smo pod lupo s fluorescentnimi filtri opazovali vpliv `kin` in `nonkin` interakcij med različnimi fluorescentno označenimi sevi B. subtilis na zasedanje površine z rojenjem. Pokazali smo, da mešanica `kin` sevov skupaj zasede površino in tvori skupne roje, medtem ko se pri ´nonkin` mešanici sevi medsebojno izključujejo, največkrat je možno zaznati le enega od obeh sevov. Razmerje med sevi v začetni mešanici pri `nonkin` kombinaciji sevov vpliva na to, kateri sev bo bolj uspešno zasedel površino. V nekaterih primerih smo zaznali segregacijo oz. prostorsko ločeno rojenje dveh `nonkin` sevov po agarni plošči. Pojavnost le-te se je povečala, če smo začetni inokulum mešanice celic redčili. Mutacija v genu comQ, ki ima pomembno vlogo pri zaznavanju kvoruma, pri sevu PS-216 ne vpliva na zmožnost tvorbe skupnega roja oz. prepoznavanja med sevi. Mešanica mutante PS-216 comQ z `nonkin` sevom kaže celo na večjo kompetitivnost oz. učinkovitost mutiranega seva pri zasedanju površine v primerjavi z njegovim divjim tipom. Microbes cooperate with each other in the utilization of nutrients from the environment, mobility, virulence, iron accumulation, mutual protection, etc. The ability to identify related organisms (`kin`) and / or discriminate less related (‘nonkin’) is important for the evolutionary success of cooperation. As part of the master's thesis, we observed the swarming pattern of more or less related mixtures of Bacillus subtilis strains on semi-solid agar medium. If the two bacterial strains are not related / compatible, antagonistic interactions and competition for surface colonization occur. In our experiments `kin` and `nonkin` interactions between different fluorescently labeled (YFP or mKate2) strains of B. subtilis were observed under the stereomicroscope with fluorescent filters. We confirmed that, when occupying the surface, the mixture of `kin` strains forms joint swarms, whereas in the `nonkin` strain combination the strains are mutually exclusive in most cases only one of the two strains can be detected. The ratio between the ‘nonkin’ strains in the initial mixture determines which strain will swarm more successfully on the surface. In some cases, we have detected segregation or spatially separated swarms of two `nonkin` strains on agar plate. The incidence of segregation increased when the initial inoculum of the cell mixture was diluted. Mutation in the comQ gene, which plays an important role in quorum sensing, does not affect the ability to form a common swarm with PS-216 wild type strain. Moreover, mixing the PS-216 comQ mutant with a `nonkin` strain indicated even greater efficiency of the mutant strain to colonize the surface as compared to its wild type. |
