Biology subjects

Postma, J.

Publications and source records attributed to Postma, J..

3 recordsLinked to original sources

bioRxiv2023

Mechanisms of extracellular electron transfer in anaerobic methanotrophic archaea

Anaerobic methanotrophic (ANME) archaea are environmentally important uncultivated microorganisms mitigating the release of the potent greenhouse gas methane. During methane oxidation ANME archaea engage in extracellular electron transfer (EET) with other microorganisms, metal oxides, and electrodes, through a currently unknown mechanism. To shed light on this mechanism, we cultivated ANME-2d archaea (Ca. Methanoperedens) in bioelectrochemical systems and observed strong methane-dependent current (91-93% of total current) associated with high enrichment of Ca. Methanoperedens on the anode (up to 82% of the community) determined by metagenomics and transmission electron microscopy. Electrochemistry and metatranscriptomics indicated that the EET mechanism was similar at various electrode potentials pointing to the involvement of an so far uncharacterized short-range electron transport protein complex and OmcZ nanowires, suggesting a unique EET pathway in all ANME-2 archaea. Our findings furthermore indicate that bioelectrochemical cells might be powerful tools for the cultivation, and possibly isolation, of uncultured electroactive microorganisms.

microbiology↗

bioRxiv2023

Rhizoctonia solani disease suppression: addition of keratin-rich soil amendment leads to functional shifts in soil microbial communities

Promoting soil suppressiveness against soil borne pathogens could be a promising strategy to manage crop diseases. One way to increase pathogen suppression would be the addition of soil organic amendments, however the mechanism behind this effect remains unexplored. The presented study will focus on Rhizoctonia solani disease in sugar beet grown in two different soils. We aim to find how microbial communities and their molecular functions can be linked to Rhizoctonia solani disease suppression in sugar beet seedlings after soil is amended with a keratin-rich side stream from the farming industry. Amended soil samples were analyzed using shotgun metagenomics sequencing, and the disease score of plants infected with Rhizoctonia and grown in the same soil was collected. Results showed that both keratin-rich amended soils were rich in bacteria from the Flavobacteriaceae, Sphingobacteriaceae, Boseaceae, Phyllobacteriaceae, Caulobacteraceae, Oxalobacteraceae, Comamonadaceae, Rhodanobacteraceae and Steroidobacteraceae, as well as taxa from the phylum Bdellovibrionota, containing obligate predatory bacteria. The only fungal group that increased significantly was the Mortierellaceae family. Keratinases were abundant in the keratin-rich amended samples. Pfam domain enrichment analysis showed a decline in domains that could be annotated in both keratin-rich amended soils (Lisse [~]18% and Vredepeel [~]30%), showing an increase in unknown proteins. Among proteins that were enriched were those potentially involved in the production of secondary metabolites/antibiotics, proteins involved in motility, keratin-degradation, and contractile secretion system proteins (mostly type VI secretion system). These results could show that keratin-rich soil amendments can support the transformation into a disease suppressive soil by stimulating the same taxa that have been found in other disease suppressive soils. We hypothesize that these taxa are responsible for the suppression effect due to their genomic potential to produce antibiotics, secrete effectors via the contractile secretion system, and degrade oxalate, which is considered a virulence factor of R. solani, while simultaneously possessing the ability to metabolize keratin.

microbiology↗

bioRxiv2022

Pinpointing the distinctive impacts of ten cover crop species on the resident and active fractions of the soil microbiome

Cover crops are used in agriculture to minimise soil erosion, prevent nutrient leaching and increase soil organic matter content. Cover crops can also be grown to stimulate the soil microbial community to improve soil biological conditions. Despite their widespread use, little is known about the impact of different cover crop species on the composition and activity of the soil microbiome. Here we investigate the effect of distinct cover crop species on the rhizosphere microbiome and to characterise both the resident (DNA-based) and the active (RNA-based) fractions of the bacterial, fungal, protist and metazoan communities in the cover crops rhizosphere. We conducted a field experiment using 70-litre bottomless containers in which we grew ten monocultures of commonly used cover crop species belonging to five plant families, and an unplanted control treatment (fallow). The total DNA and RNA were extracted from soil and the bacterial, fungal, protistan and metazoan communities were characterized using Illumina MiSeq sequencing. We found that all cover crop species significantly impacted the resident and active microbial community composition. Moreover, cover crops showed distinct selection strengths on their rhizospheres. Together with borage (Boraginaceae), oilseed radish (Brassicaceae) was shown to provoke the strongest microbial shifts, in part attributable to a promotion of the bacterial family Pseudomonadaceae and a repression of Microascaceae in the rhizosphere. Lentil (Fabaceae) showed enrichment in fungal taxa, including Trichocomaceae and fungal members of the Glomerales order, whereas black oat, hybrid ryegrass (both Poaceae) and marigold (Asteraceae) induced relatively mild changes in the soil microbial communities. Predominantly, differences in selection strengths were consistent among the four organismal groups under investigation and were observed in both the active and resident communities. Our work provides a broad baseline for the effects of cover crops on four organismal groups, which may facilitate future cover crop selection to advance soil health.

ecology↗