Significance Of Microbial Community Structure For Horticulture Systems

Role of Microbial Indicators in Evaluating Australian Agriculture and Horticulture Systems

Discuss about the Significance of Microbial Community Structure for Hotriculture Systems.

Evidence-based research literature confirms the attribution of microorganisms in terms of effectively maintaining the quality and productivity of soils of various geographical regions (Sharma, et al., 2010). Microbial community maintains significant agricultural processes including pollutants degradation, structural dynamics of soil as well as regulation of the fundamental nutrients. Microbial indicators require analysis at the individual level, population level, functional (group) level, community level and ecosystem level for exploring the soil enzymes, denitrification, nitrogen mineralization, basal respiration rate as well as the microbial biomass (Sharma, et al., 2010). The research findings by (Bissett, et al., 2016) indicate the requirement of nitrogen in the soil for tenure of six months in the context of cultivating the crops near the Australian coastal regions. The microbes in the Australian soil facilitate the conversion of soil fertilizer to nitrous oxide that evidentially leads to environmental deterioration (Bissett, et al., 2016). The research data confirms the genetic adaptability of soil microorganisms in terms of utilizing nitrogen for accomplishing their nutritional requirements. The presence of Nif genes and diazotrophic microbes in the Australian soil is an indicator of its nitrogen fixing capacity. Such type of soil appears beneficial for cultivating the crops in the Australian environment. Genome analysis of the microbial community in the Australian soil reveals the existence of rRNA sequences in the 16S rRNA and 18S rRNA genes (Bissett, et al., 2016).

The pattern of consistent soil cultivation in the Australian regions reduces its microbial elements that reciprocally decrease its quality as well as nutritional abundance. Analysis of Australian soil reveals the following facts regarding the highest concentration of various microorganisms in the arid, continental, temperate and tropical regions (Trivedi, Delgado-Baquerizo, Anderson, & Singh, 2016).            

The root exudates of various plants species influence the concentration of the microbial community in the Australian soil. These exudates include amino acids, organic acids and carbohydrates (Gourmelon, et al., 2016). The soil of the elevated concentration of potassium/magnesium ratio remains dominated with the formations of Tristaniopsis. The dispersal limitations of the Australian soil prove to be the deciding factors in relation to the development of microbial communities. Thus, the quality of the soil derives from its dispersal limitations under the influence of geographical and environmental factors. The development of Actinobacteria in the Australian soil is based on the direction of wind flow that effectively facilitates its dispersal (Eisenlord, Zak, & Upchurch, 2012). Ecological forces including climatic alteration and edaphic attributes reciprocally facilitate the propagation of Actinobacteria in the soil of arid and temperate systems. The change in weather influences the pattern of C: N ratio in the soil as well as distance and time variations proves to be the deciding factors for the dispersion of Actinobacteria in the oldest soil. The variation between decay and observed distance over the course of time influences the abundance of 16S rRNA genes of Actinobacteria in the soil environment (Eisenlord, Zak, & Upchurch, 2012).

Key Microbial Species and their Distribution in Australian Soil

Evidence-based findings by (Miyashita, 2015) indicate the influence of evolutionary history of soil as well as associated microbes and environmental factors above the ground as the contributory factors that facilitate the development of Betaproteobacteria and Alphaproteobacteria classes. The topology of trees as well as the magnesium content and C:N ratio of the soil influence the variance of proteobacteria in the continental and tropical regions. Contrarily, the association of Acidobacteria in soil varies in accordance with the alteration of its pH. However, other physicochemical properties of the soil do not influence the distribution of Acidobacteria under its layers (Miyashita, 2015). The metagenomic and genomic information substantiate the ecological capacity of Acidobacteria in terms of utilizing nitrogen sources and exhibiting response against soil acidity as well concentration of micro and macronutrients (Kielak, Barreto, Kowalchuk, Veen, & Kuramae, 2016). Agrobacterium proves to be the source of EPS (exopolysaccharide) production through the expression of various active transporters. These bacteria also facilitate the active degradation of gellan gum and induce competitive mechanisms for improving the health and quality of soil structure. Nitrogen reduction capacity of Acidobacteria attributes to their nirA gene that assists in the encoding of nitrate reductase for the effective transformation of nitrate to nitrite that further reduces to glutamate and ammonia (Kielak, Barreto, Kowalchuk, Veen, & Kuramae, 2016). Different strains of Acidobacteria including ATCC51196, Ellin345, MP5ACTX8, MP5ACTX9, SP1PR4, DSM23119, ELLIN6076, K22, MP-01, DSM6591 and TMBS4 contain transporter systems that assist in the configuration of substrate categories attributing to anions, cations, siderophores, peptides and amino acids (Kielak, Barreto, Kowalchuk, Veen, & Kuramae, 2016). The transformation of these ingredients gives an added advantage to Acidobacteria in terms of acquiring sustainability in oligotropic soil conditions. This rationally enhances the cultivation capacity of soil in the continental and tropical systems.

The research findings by (Navarrete, et al., 2015) reveal the inverse relationship between the structure and composition of Verrucomicrobial community and the nutritional content and associated fertility of the Australian continental soil. The soil fertility factors including the concentration of potassium, magnesium, calcium, phosphorus and total nitrogen influence the abundance of Verrucomicrobia in the continental agricultural and natural systems (Navarrete, et al., 2015). Verrucomicrobia evidentially interact with the plants roots as well as chemical factors in the soil. The abundance of Verrucomicrobia is directly related to the reduced nitrogen availability in the soil if the continental system. Verrucomicrobia remain increasingly dependent on the organic matter in soil. The r-selected and k-selected Verrucomicrobia exhibit elevated and decreased growth rates based on the nutritional uptake mechanisms and substrate affinities of the forest and as well the deforested soils (Navarrete, et al., 2015). In conclusion, the limited nutrient availability of the Australian continental soil is indicated by the abundance of Verrucomicrobia community. The research analysis by (Trivedi, Delgado-Baquerizo, Anderson, & Singh, 2016) confirms the increased abundance of Chloroflexi in the soils of the agricultural system in comparison to the natural soil system in the Australian subcontinent. The chemical and biophysical heterogeneity of the agricultural soil system facilitates the growth of Chloroflexi in the temperate and arid regions. Unlike Acidobacteria, Chloroflexi does not grow well in the natural soil system; however, its abundance in agricultural soil is a potential indicator of soil’s nutritional capacity (Trivedi, Delgado-Baquerizo, Anderson, & Singh, 2016). Firmicutes develop under the influence of thawed environment in permafrost soil. The thawed atmosphere induces the Firmicutes genes that encode hydrolases decompose the ether bonds of dead bacterial biomass in permafrost soil. This makes Firmicutes as the greatest indicators of microbial development and responses in the thawed soils. However, Cyanobacteria utilize amino acids and oligopeptides in terms of nitrogen sources in permafrost soil for effectively assimilating the organic compounds during the process of biosynthesis. The appearance of Cyanobacteria in the layers of soil (after thaw) is confirmed by the increased activity of their genes with the objective of producing ammonia from nitrate across the spring sediments. Microbial activity in the permafrost thaw is measured by determining the pH fluctuation in the thawed soil. This activity rationally indicates the generation of greenhouse gases under the influence of microbial decomposition in the permafrost soil.

Conclusion

The analysis of the microbial community structure and prevalence across the agricultural and natural soil systems is necessarily required with the objective of testing their cultivation capacity. Microbial variation in different soil regions proves to be a significant indicator that assists in determining the quality of soil in the Australian horticultural and agricultural systems.

References

Bissett, A., Fitzgerald, A., Meintjes, T., Mele, P. M., Reith, F., Dennis, P. G., . . . Young, A. (2016). Introducing BASE: the Biomes of Australian Soil Environments soil microbial diversity database. Gigascience.

Eisenlord, S. D., Zak, D. R., & Upchurch, R. A. (2012). Dispersal limitation and the assembly of soil Actinobacteria communities in a long-term chronosequence. Ecology and Evolution, 2(3), 538-549. doi:10.1002/ece3.210

Gourmelon, V., Maggia, L., Powell, J. R., Gigante, S., Hortal, S., Gueunier, C., . . . Carriconde, F. (2016). Environmental and Geographical Factors Structure Soil Microbial Diversity in New Caledonian Ultramafic Substrates: A Metagenomic Approach. PLoS One.

Kielak, A. M., Barreto, C. C., Kowalchuk, G. A., Veen, J. A., & Kuramae, E. E. (2016). The Ecology of Acidobacteria: Moving beyond Genes and Genomes. Frontiers in Microbiology. doi:10.3389/fmicb.2016.00744

Miyashita, N. T. (2015). Contrasting soil bacterial community structure between the phyla Acidobacteria and Proteobacteria in tropical Southeast Asian and temperate Japanese forests. Genes & Genetic Systems, 61-77. doi:https://doi.org/10.1266/ggs.90.61

Navarrete, A. A., Soares, T., Rossetto, R., Veen, J. A., Tsai, S. M., & Kuramae, E. E. (2015). Verrucomicrobial community structure and abundance as indicators for changes in chemical factors linked to soil fertility. Antonie Van Leeuwenhoek, 741-752. doi:10.1007/s10482-015-0530-3

Sharma, S. K., Ramesh, A., Sharma, M. P., Joshi, O. P., Govaerts, B., Steenwerth, K. L., & Karlen, D. L. (2010). Microbial Community Structure and Diversity as Indicators for Evaluating Soil Quality. Biodiversity, Biofuels, Agroforestry and Conservation Agriculture, 317-358.

Trivedi, P., Delgado-Baquerizo, M., Anderson, I. C., & Singh, B. K. (2016). Response of Soil Properties and Microbial Communities to Agriculture: Implications for Primary Productivity and Soil Health Indicators. Frontiers in Plant Science.