Biology subjects

Richnow, H. H.

Publications and source records attributed to Richnow, H. H..

3 recordsLinked to original sources

bioRxiv2024

Stable isotopes and nanoSIMS single-cell imaging reveals soil plastisphere colonizers able to assimilate sulfamethoxazole

The presence and accumulation of both plastics and antibiotics in soils may lead to the colonization, selection and propagation of bacteria with certain metabolic traits e.g. antibiotic resistance, in plastisphere. However, the impact of plastic-antibiotic tandem on the soil ecosystem functioning, particularly on microbial function and metabolism remains currently unexplored. Herein, we investigated the competence of soil bacteria to colonize plastics and to mineralize/degrade 13C-labelled sulfamethoxazole (SMX). Using single cell imaging, isotope tracers, soil respiration and SMX mineralization bulk measurements we show that microbial colonization of polystyrene (PE) and polyethylene (PS) surfaces takes place within the first 30 days of incubation. Morphologically diverse, microorganisms were colonizing both plastic types, with a preference for PE substrate. Nano-scale Secondary Ion Mass Spectrometry measurements show that 13C enrichment was highest at 130 days with values up to 1.29 atom %, similar to those of the 13CO2 pool (up to 1.26 atom%, or 22.55 {per thousand}). Our results provide direct evidence demonstrating, at single cell level, the capacity of bacterial colonizers of plastics to assimilate 13C from 13C-SMX. These findings expand our knowledge on the role of plastisphere microbiota in the ecological functioning of soils impacted by anthropogenic stressors.

microbiology↗

bioRxiv2021

High-Resolution Chemical Mapping and Microbial Identification of Rhizosphere using Correlative Microscopy

During the past decades, several stand-alone and combinatory methods have been developed to investigate the chemistry (i.e. mapping of elemental, isotopic and molecular composition) and the role of microbes in soil and rhizosphere. However, none of these approaches are currently capable of characterizing soil-root-microbe interactions simultaneously in their spatial arrangement. Here we present a novel approach that allows chemical and microbial identification of the rhizosphere at micro-to nano-meter spatial resolution. Our approach includes i) a resin embedding and sectioning method suitable for simultaneous correlative characterization of Zea mays rhizosphere, ii) an analytical work flow that allows up to six instruments/techniques to be used correlatively, and iii) data and image correlation. Hydrophilic, immunohistochemistry compatible, low viscosity LR white resin was used to embed the rhizosphere sample. We employed waterjet cutting and avoided polishing the surface to prevent smearing of the sample surface at nanoscale. Embedding quality was analyzed by Helium Ion Microscopy (HIM). Bacteria in the embedded soil was identified by Catalyzed Reporter Deposition-Fluorescence In Situ Hybridization (CARD-FISH) to avoid interferences from high levels of auto fluorescence emitted by soil particles and organic matter. Chemical mapping of the rhizosphere was done by Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray analysis (SEM-EDX), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), nano-focused Secondary Ion mass Spectrometry (nanoSIMS), and confocal Raman spectroscopy ({micro}-Raman). High-resolution correlative characterization by six different techniques followed by image registration shows that this method can meet the demanding requirements of multiple characterization techniques to chemically map the rhizosphere and identify spatial organization of bacteria. Finally, we presented individual and correlative workflows for imaging and image registration to analyze data. We hope this method will be a platform to combine various 2D analytics for an ample understanding of the rhizosphere processes and their ecological significance. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/429689v2_ufig1.gif" ALT="Figure 1"> View larger version (130K): org.highwire.dtl.DTLVardef@16c8234org.highwire.dtl.DTLVardef@d84266org.highwire.dtl.DTLVardef@1ef6001org.highwire.dtl.DTLVardef@87f51c_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2017

Conductive particles enable syntrophic acetate oxidation between Geobacter and Methanosarcina from coastal sediments

Coastal sediments are rich in conductive minerals, which could impact microbial processes for which acetate is a central intermediate. In the methanogenic zone, acetate is consumed by methanogens and/or syntrophic acetate oxidizing (SAO) consortia. SAO consortia live under extreme thermodynamic pressure and their survival depends on successful partnership. Here we demonstrate that conductive minerals facilitate a SAO partnership between Geobacter and Methanosarcina from the coastal sediments of the Bothnian Bay, Baltic Sea. Bothnian methanogenic sediments showed a high apparent isotopic fractionation (c 1.07) characteristic of CO2-reductive methanogenesis. The native community was represented by electrogens such as Geobacter and methanogens like Methanosarcina. Upon the addition of conductive particles (activated carbon and magnetite) methanogenesis from acetate increased four fold. Geobacter (96% related to G. psychrophilus) and Methanosarcina (99% related to M. subterranea) dominated the conductive particle-spiked SAO communities. Using NanoSIMS we demonstrated that during SAO, Geobacter incorporated 82% of the labeled acetate as compared to only 18% by Methanosarcina. At the same time Geobacter converted 27% of the 13C-acetate to 13CO2 as detected by IRMS. Indigenous soluble shuttles were not involved in SAO, since spiking fresh cultures with spent-media filtrate had no effect on methanogenic rates. Our results demonstrate that Geobacter oxidizes acetate to CO2 while transferring electrons extracellularly via conductive particles to Methanosarcina, which utilizes them for CO2 reduction to methane. In natural environments, mediation of SAO by conductive particles between electrogens and methanogens could impact the iron and methane cycles.\n\nSignificanceAcetate oxidizing bacteria are known to thrive in mutualistic consortia in which H2 or formate is shuttled to a methane-producing Archaea partner. Here we discovered that they could instead transfer electrons via conductive minerals. Mineral-SAO (syntrophic acetate oxidation) could be a vital pathway for CO2-reductive methanogenesis in the environment, especially in sediments rich in conductive minerals. Mineral-SAO is therefore of potential importance for both iron and methane cycles in sediments and soils. Additionally, our observations imply that agricultural runoff or amendments with conductive chars could trigger a significant increase in methane emissions.

microbiology↗