Metagenomic sequencing and binning reveal carbon cycling microorganisms and gene functions in park environments

In the midst of increasing global warming and accelerated urbanization, urban parks, serving as significant carbon sinks, are increasingly recognized for their role in mitigating the urban heat island effect. However, limited research investigating the urban park carbon cycle hinders our full understanding and effective use of their carbon sink potential. This study employed metagenomics sequencing and 16S rRNA gene sequencing to characterize the carbon cycle and its influencing factors within soil and water from collected from nine city parks. Notably, the abundance and alpha diversity of carbon cycle microbes and genes were higher in soil compared to water. Specifically, soil samples exhibited enrichment of carbon cycling genes involved primarily in polysaccharide metabolism, particularly those associated with starch and cellulose metabolism. Conversely, water samples, revealed a greater prevalence of genes associated with chitin metabolism. The most important factor affecting soil carbon cycling genes was bacterial community, followed by non-nutritional factors and nutrient factors, while heavy metals demonstrated no effect on soil carbon cycling genes. The most important factor affecting water carbon cycling genes was only bacterial community. The analysis yielded 381 high-quality metagenomic assembled genomes (MAGs) containing carbon cycling genes, with significant covariation observed between the pta and carbon cycling genes ackA and acyP, which encode cellulose degradation functions. These findings contribute to a better understanding of microbial carbon metabolism within urban parks and offer a foundation for effective carbon emission management strategies.