Urbanization reduces overall cyanobacterial abundance but favors heterocystous forms

Managing agricultural land, both in terms of quantity and quality, is one of the major challenges of the world. Urbanization is a powerful human-induced land use transformation that not only affects adversely the availability of arable lands, but also the soil microbial diversity crucial for maintaining fertility and other soil functions. The study reports the change in cyanobacterial diversity and community composition along a rural-urban gradient, through amplicon sequencing using Illumina MiSeq approach. Urbanization significantly altered the diversity, abundance and community composition of cyanobacteria that vary along the gradient. Rural soils had the highest diversity and maximal abundance of uncultured cyanobacteria, followed by sub-urban and urban soils. In general, along the gradient Oscillatoriales (non-heterocystous forms) were the most abundant taxa, while abundance of Nostocales (i.e., heterocyst bearing N2-fixers) increased in the urban soil. The favored growth of specific taxa in urban soils indicates biotic homogenization. The relative dominance of genus Leptolyngbya in urban and sub-urban soils could be used as an indicator of urbanization.