Changing the Cultivability of Soil Bacteria with the Addition of Growth Factors

Introduction. Currently, approximately 1% of all known bacteria can be cultivated under laboratory conditions. The inability to obtain pure cultures of many microorganisms creates significant challenges for fundamental and applied research. This is particularly true for soil bacteria because of the high diversity of prokaryotic species in this environment. These findings highlight the need to develop methods for cultivating new strains, including the development of new culture media and modification of existing media by adding growth factors. The aim of this study is to investigate the possibility of increasing bacterial cultivability by adding growth factors such as heme and potassium humate to the R2A medium, as well as replacing agar-agar with gellan gum.

Materials and Methods. The study involved soils from anthropogenic landscapes in the Rostov Region. The effects of growth factors on the cultivability of soil bacteria were investigated by counting the total number of colonies on a universal culture medium and separately recording fast-growing and slow-growing strains. The data obtained were processed using Statistica.

Research Results. According to the results, potassium humate has a stimulating effect at low concentrations and an inhibitory effect at high concentrations. Heme increases the growth rate of fast-growing strains while simultaneously inhibiting slow-growing bacteria. Gellan gum improved the cultivability of slow-growing strains in one experimental variant.

Discussion and Conclusion. Given the ambiguous results regarding the effects of gellan gum and heme, further experiments with these components are needed. However, potassium humate stimulated bacterial growth. Based on these data, it can be concluded that the addition of growth factors may enable the cultivation of previously uncultivated soil bacteria. Thus, this topic is a promising area in experimental microbiology and requires further similar research.

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