Humic substances interacting with organisms, including microorganisms, are capable of suppressing their development with an increased content. In a number of works, an increase in the growth of microorganisms of different physiological groups under the influence of humates has been shown. In this regard, a promising line of research is the study of the effect of humate preparations on the growth of alkanotrophic microorganisms on hydrocarbon substrates, which can be used to intensify the processes of bioremediation of oil-contaminated media. It was shown that the humic preparation "Flexom" stimulated the growth of the hydrocarbon-oxidizing bacteria Acinetobacter sp. Humic acids intensified the growth of Rhodococcus erythropolis on phenol.
The effect of growth stimulation with humates can also be used in biotechnology of bacterial plant protection products from harmful insects. There is evidence that humate in certain concentrations not only contributed to an increase in cell titer, but also accelerated the processes of spore and toxin formation in entomopathogenic bacteria Bacillus thuringiensis.
The purpose of this work was to study the effect of the “Powhumus” humate preparation on the growth of B. thuringiensis ssp. kurstaki.
The objects of the study were B. thuringiensis ssp. kurstaki (from the collection of O.F. Vyatchina, Department of Microbiology, ISU).
To determine the effect of the preparation "Powhumus" on the growth of the B. thuringiensis strain, the LB medium of the following composition (%) was used: peptone - 1.0; yeast extract - 0.5; NaCl - 1.0. Humate was added to the media at concentrations: 0.0001; 0.001; 0.01; 0.1 and 1%. LB medium without humate was used as a control. The cultivation was carried out in flasks (250 ml) with 100 ml of LB medium. The media were inoculated with a one-day culture suspension (1% of the total volume) and incubated under stationary conditions for 24 h at 30 ° C. Quantitative registration of microorganisms was carried out using the method of limiting dilutions.
Studies have shown that in the LB medium without the addition of humate, the number of cells of the studied B. thuringiensis strain increased by almost an order of magnitude during 24 hours of cultivation - from (2.75 ± 0.45) 107 to (3.35 ± 0.45) 108 CFU / ml. When 0.01% humate was added to the nutrient medium, the number of B. thuringiensis cells was almost three times higher than in the control ((9.05 ± 0.55) 108 and (3.35 ± 0.45) 108 CFU / ml, respectively).
Humate at a concentration of 0.0001; 0.001 and 0.1% had no significant effect on the growth of the B. thuringiensis strain.
The suppression of culture growth was noted during cultivation in a medium with 1% humate. At the same time, the number of cells was more than two times lower than in the control.
Thus, humate concentrations have been revealed that stimulate the growth of the entomopathogenic bacterium B. thuringiensis ssp. kurstaki (0.01%), as well as the humate content, at which it had no visible effect on the growth of the strain (0.0001; 0.001 and 0.1%). The concentration limit was established, above which the growth inhibition of B. thuringiensis (1%) was observed. The revealed ranges of the effective concentrations of humate should be taken into account when using these substances in the biotechnology of plant protection against phytopathogens.
This work was supported by the RFBR grant 19-29-05213 MK "Mechanisms of the complex interaction of soils with oil, oil products and surfactants in the processes of oil pollution and bioremediation".
|Affiliation of speaker||ФГБОУ ВО "Иркутский государственный университет"|
|Publication||IOP Conference Series: Earth and Environmental Science|