Project description:This project aims to investigate the metabolic pathways expressed by the active microbial community occurring at the deep continental subsurface. Subsurface chemoLithoautotrophic Microbial Ecosystems (SLiMEs) under oligotrophic conditions are supported by H2; however, the overall ecological trophic structures of these communities are poorly understood. Some deep, fluid-filled fractures in the Witwatersrand Basin, South Africa appear to support inverted trophic pyramids wherein methanogens contributing <5% of the total DNA apparently produce CH4 that supports the rest of the community. Here we show the active metabolic relationships of one such trophic structure by combining metatranscriptomic assemblies, metaproteomic and stable isotopic data, and thermodynamic modeling. Four autotrophic β-proteobacteria genera that are capable of oxidizing sulfur by denitrification dominate. They co-occur with sulfate reducers, anaerobic methane oxidizers and methanogens, which each comprises <5% of the total community. Defining trophic levels of microbial chemolithoautotrophs by the number of transfers from the initial abiotic H2-driven CO2 fixation, we propose a top-down cascade influence of the metabolic consumers that enhances the fitness of the metabolic producers to explain the inverted biomass pyramid of a multitrophic SLiME. Symbiotic partnerships are pivotal in the deep biosphere on and potentially beyond the Earth.
Project description:Multispecies biofilms are the predominant form of bacterial growth in natural and human-associated environments. Although the pathways involved in monospecies biofilm have been well characterized, less is known about the metabolic pathways and emergent traits of a multispecies biofilm community. Here, we performed a transcriptome survey of the developmental stages of a 3-species biofilm community and combined it with quantitative imaging and growth experiments. We report the remodelling of central metabolism of two of the three species in this community. Specifically, we observed an increase in the expression of genes associated with glycolysis and pentose phosphate pathways in K. pneumoniae. Similarly, a decrease in the expression of the same pathways in P. protegens was observed along with an increase in expression of glyoxalate cycle genes when grown as a mixed species biofilm, suggesting reorganisation of metabolic pathways and metabolite sharing for the community biofilms. To test the possibility of cross-feeding for the community, planktonic growth experiments revealed that both the Pseudomonads grew well in TCA cycle intermediates, while K. pneumoniae grew poorly when given those carbon sources. Despite this poor growth in mono-culture, K. pneumoniae was still the dominant species in mixed species biofilms cultivated in TCA intermediates as the sole source of carbon. The biofilm growth data, combined with the transcriptomics data, suggests there is reorganisation of metabolism for the community members and may allow for cross-feeding that allows K. pneumoniae to dominate the community. We also demonstrated that sdsA1 of P. aeruginosa was induced upon exposure to the surfactant SDS and that this gene was essential in protecting mono and mixed species biofilms from surfactant stress. This also suggests that the community members can share defence mechanisms. Overall, this study describes a comprehensive transcriptomics level investigation of shared resources, metabolites and stress defence that may underpin the emergent properties of mixed species biofilm communities.
Project description:We compared genetic profiles of planktonic stage to biofilm stage of deep sea bacterium Pseudoalteromonas sp. SM9913 and revealed genetic features during switch from planktonic to pellicle stage in Pseudoalteromonas sp. SM9913.
Project description:P. aeruginosa PA14 mutant strain PA4496 expression in biofilm cells relative to PA14 wild-type strain expression in biofilm cells. All samples cultured in LB with glass wool
Project description:Fungi have an important role in nutrient cycling in most ecosystems on Earth, yet their ecology and functionality in deep continental subsurface remain unknown. Here, we report the first observations of active fungal colonization of mica schist in the deep continental biosphere and the ability of deep subsurface fungi to attach to rock surfaces under in situ conditions in groundwater at 500 and 967 m depth in Precambrian bedrock. We present an in situ subsurface biofilm trap, designed to reveal sessile microbial communities on rock surface in deep continental groundwater, using Outokumpu Deep Drill Hole, in eastern Finland, as a test site. The observed fungal phyla in Outokumpu subsurface were Basidiomycota, Ascomycota, and Mortierellomycota. In addition, significant proportion of the community represented unclassified Fungi. Sessile fungal communities on mica schist surfaces differed from the planktic fungal communities. The main bacterial phyla were Firmicutes, Proteobacteria, and Actinobacteriota. Biofilm formation on rock surfaces is a slow process and our results indicate that fungal and bacterial communities dominate the early surface attachment process, when pristine mineral surfaces are exposed to deep subsurface ecosystems. Various fungi showed statistically significant cross-kingdom correlation with both thiosulfate and sulfate reducing bacteria, e.g., SRB2 with fungi Debaryomyces hansenii.
Project description:Biofilms are ubiquitous in natural, medical, and engineering environments. While most antibiotics that primarily aim to inhibit cell growth may result in bacterial drug resistance, biofilm inhibitors do not affect cell growth and there is less chance of developing resistance. This work sought to identify novel, non-toxic and potent biofilm inhibitors from Streptomyces bacteria for reducing the biofilm formation of Pseudomonas aeruginosa PAO1. Out of 4300 Streptomyces strains, one species produced and secreted peptide(s) to inhibit P. aeruginosa biofilm formation by 93% without affecting the growth of planktonic cells. Global transcriptome analyses (DNA microarray) revealed that the supernatant of the Streptomyces 230 strain induced phenazine, pyoverdine, and pyochelin synthesis genes. Electron microscopy showed that the supernatant of Streptomyces 230 strain reduced the production of polymeric matrix in P. aeruginosa biofilm cells, while the Streptomyces species enhanced swarming motility of P. aeruginosa. Therefore, current study suggests that Streptomyces bacteria are an important resource of biofilm inhibitors as well as antibiotics.