Freshwater reservoirs emit greenhouse gases (GHGs) such as methane (CH4) and carbon dioxide (CO2), contributing to global warming, mainly when impacted by untreated sewage and other anthropogenic sources. These gases can be produced by microbial organic carbon decomposition, but little is known about the microbiota and its participation in GHG production and consumption in these environments. In this paper we analyzed the sediment microbiota of three eutrophic tropical urban freshwater reservoirs, in different seasons and evaluated the correlations between microorganisms and the atmospheric CH4 and CO2 flows, also correlating them to limnological variables. Our results showed that deeper water columns promote high methanogen abundance, with predominance of acetoclastic Methanosaeta spp. and hydrogenotrophs Methanoregula spp. and Methanolinea spp. The aerobic methanotrophic community was affected by dissolved total carbon (DTC) and was dominated by Crenothrix spp. However, both relative abundance of the total methanogenic and aerobic methanotrophic communities in sediments were uncoupled to CH4 and CO2 flows. Network based approach showed that fermentative microbiota, including Leptolinea spp. and Longilinea spp., which produces substrates for methanogenesis, influence CH4 flows and was favored by anthropogenic pollution, such as untreated sewage loads. Additionally, less polluted conditions favored probable anaerobic methanotrophs such as Candidatus Bathyarchaeota, Sva0485, NC10, and MBG-D/DHVEG-1, which promoted lower gaseous flows, confirming the importance of sanitation improvement to reduce these flows in tropical urban freshwater reservoirs and their local and global warming impact.

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The demand for the increased productivity of sugarcane crops has required changes in its production chain, such as the use of pre-sprouted seedlings (PSS) of sugarcane into the chain. In this system, the inoculation of beneficial microorganisms, such as plant growthpromoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF), can improve seedling development. The objective was to evaluate the beneficial effect of PGPB and AMF inoculation on sugarcane PSS production system. Experiments were carried out in greenhouse using a commercial substrate with different levels of fertilization to evaluate the plant biomass and nutritional status. The bacteria strains are able to produce indole acetic acid and to amplify the nifH gene. The coinoculation of strains IAC-BeCa-095 with AMF (Glomus macrocarpum and Glomus etunicatum) improved the plant shoot biomass (25%) on the fertilized substrate. The strains IAC-BeCa-088 (Burkholderia caribensis), IAC-RBca5 (Pseudomonas sp.) and IAC-RBca10 (Bacillus sp.) without AMF and fertilization improved the shoot biomass by up to 35%. Coinoculation with strain IAC-BeCa-095 (Kosakonia radicincitans) and AMF improved the shoot and root biomass by up to 27 and 75%, respectively, in the conventionally fertilized substrate, demonstrating a synergistic effect of these microorganism consortia. The use of beneficial microorganisms may be a viable practice in the production of PSS sugarcane. Moreover, this study is the first to demonstrate the synergistic effect of endophytic bacteria (K. radicincitans) or rhizobacteria (Bacillus sp.) with AMF and Pseudomonas sp. or B. caribensis, without AMF inoculum on the production of sugarcane PSS to improve plant growth and plant nutrition.

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