| Predation,as a major mode of interaction in ecosystems,is an important driving force in the construction and evolution of biological communities,and is an indispensable link in the global elemental cycle.Recent exploitation and utilization of marine microbial resources have shown that marine predatory bacteria can regulate the construction of marine microbial communities,therefore,exploring the predation strategies of marine predatory bacteria can help to deepen the understanding of the evolution of marine microbial communities.Based on the nine isolated strains of Bradymonabacteria,a new group of predatory bacteria discovered in our laboratory in 2015,we conducted predation studies to clarify the predation mechanism.1.In order to obtain the optimal growth of Bradymonabacteria,its growth curve was monitored in different media.It was shown that 0.15%sodium pyruvate had a growthpromoting effect on Bradymonabacteria;Lujinxingia vulgaris TMQ2 grew the fastest,entering the exponential phase at 20 h and reaching a biomass(OD600)of 1.6.The predatory ability of Bradymonabacteria was evaluated using a mixture of bacterial broths and up-and-down inoculation.The results showed that L.sediminis TMQ1,L.sediminis TMQ3,L.sediminis SEH01T,L.litoralis B210T,L.vulgaris TMQ2,Bradymonas sediminis FA350T,Microvenator marinus V1 718T,Persicimonas caeni YN101 T belonged to medium and strong predators,and only a small portion of prey colonies remained after predation;L.vulgaris TMQ4T belonged to weak predators,and the area of prey colonies was hardly reduced after predation.2.The possible search and aggressive predation of nearby prey colonies by Bradymonabacteria in natural habitats was simulated by the movement of colonies of Bradymonabacteria toward neighboring prey colonies and predation.The results showed that the nine strains showed differences in the degree of predation,with L.sediminis TMQ1,L.sediminis SEH01 T,L.vulgaris TMQ2,L.sediminis TMQ3 and L.litoralis B210T having higher predation efficiency and predating more than half of the prey colonies;the colony sizes of the nine strains were significantly were different.In co-culture(mixed bacterial solution and upper and lower bacterial solution inoculation)predation,B.sediminis FA350T was one of the strong predators,but in adjacent predation,B.sediminis FA350T was a weak predator;colonies of B.sediminis FA350T were significantly smaller than other strong predators.The expansion of colonies of Bradymonabacteria on semi-solid and solid media surfaces was counted,and nine strains showed different colony sizes on the same surface.The results showed that the rapid gliding movement of Bradymonabacteria would promote its faster approach and invasion to the prey and improve the predation efficiency during the neighboring predation.3.The predation resistance of Vibrio parahaemolyticusATCC 17802T was analyzed by adaptive laboratory evolutionary means after passing under the predation pressure of L.vulgaris TMQ2,and G23 was found to exhibit greater predation resistance.The results of gradient dilution spot plates of G23 and G0 in nutrient-rich,oligotrophic and nutrient-free media after 4 h of predation by L.vulgaris TMQ2 showed that the number of cells remaining in G23 was significantly greater than that in G0 under oligotrophic and nutrient-free conditions,which may be due to the stronger predation pressure generated by L.vulgaris TMQ2 during nutrient deficiency,when G23 is stimulated by predation pressure to modulate itself to exhibit greater resistance to predation.Analysis of mutant loci in the G0 and G23 genomes revealed five nucleotide loci,one in the intergenic region and four in the coding region.These mutated loci may lead to aberrant expression of CheW,LysR family transcriptional regulator and superfamily 1 DNA helicases,which in turn affect the growth metabolism,chemotaxis and biofilm formation ability of G23. |
PDF Full Text Request