Biology subjects

Pietrasiak, N.

Publications and source records attributed to Pietrasiak, N..

3 recordsLinked to original sources

bioRxiv2025

Unraveling the diversity and functional potential of cyanosphere microbiomes assembled from terrestrial cyanobacteria

The cyanosphere consists of heterotrophic microorganisms residing within the exopolysaccharide sheath of cyanobacteria, acting as a crucial interface between the cyanobacteria and their surrounding environment. Understanding the interactions between cyanobacteria and their cyanospheres is essential for predicting the success of terrestrial cyanobacteria in providing ecosystem services in nutrient-poor environments. However, knowledge of the microbial diversity within the cyanosphere remains limited. In this study, we employed metagenomic sequencing to reconstruct 410 metagenome-assembled genomes (MAGs) from cyanosphere-associated microbes linked to 56 unialgal terrestrial cyanobacteria cultures, representing 12 distinct cyanobacteria orders. Our findings revealed that the composition of cyanosphere microbial communities was unique to each cyanobacterial host and was significantly shaped by environmental factors such as habitat, precipitation, and temperature from which the cultures were originally obtained. Notably, three microbial genera, Brevundimonas, Devosia, and Sphingopyxis, were present in over 30% of the cyanospheres, forming a core cyanosphere microbiome. Functional gene analysis showed a distinction between the cyanobacteria and their associated cyanospheres, with dissimilatory nitrate reduction being the dominant pathway in the cyanosphere, while nitrogen fixation was more common in the cyanobacteria. Three cyanospheres also contained nitrogen fixation genes of which two hosts were nitrogen fixation capable themselves. The cyanosphere harbored genes for polysaccharide lyases, indicating a possible link to the exopolysaccharides produced by the cyanobacteria. Given the observed variability in microbial community composition and function across different cyanobacterial hosts, future ecological assessments and restoration efforts involving cyanobacteria should not only focus on the cyanobacteria themselves but also consider their associated microbial communities. ImportanceOur study identifies members of a highly understudied, and potentially under-valued, microbial community -- the cyanosphere. We used a diversity of terrestrial cyanobacteria to understand how the cyanosphere composition and predicted functions were influenced by the host cyanobacterium and environmental factors using metagenomics. This is a new approach to study the cyanosphere and provides insights into the diversity of terrestrial microbial communities. Importantly, our results underscore the need to consider microbial consortia when assessing the ecological potential of cyanobacteria in terrestrial restoration.

ecology↗

bioRxiv2022

Exploring Viral Communities Associated With Terrestrial Cyanobacteria Metagenomes

Viruses are exceedingly common, but little is known about their diversity let alone how they behave in extreme environments, and whether viruses facilitate adaptation of their hosts to harsh conditions. To set a foundation for understanding of these understudied viral-host interactions, we created a catalog of viruses through analysis of metagenomes from 50 unialgal but nonaxenic Cyanobacteria cultures with 47 cultures isolated from various terrestrial habitats, including desert soil and rock surfaces, tropical soil, and vernal pools. These cultures represent low diversity microbial consortia dominated by the terrestrial Cyanobacteria and its associated cyanosphere microbiome containing heterotrophic microbes. We identified viral sequences in metagenomes, grouped these into viral operational taxonomic units (vOTUs) and then placed vOTUs into viral clusters (VCs). We also calculated vOTU relative abundance and predicted possible bacterial hosts. In total we predicted 814 viral sequences representing 726 vOTUs. We assigned putative taxonomy to 72 of the 814 putative viral sequences; these were distributed into 15 VCs -- mostly assigned to the recently abolished Caudovirales order (now Caudoviricetes class) of viruses. We found that nonaxenic cultures were dominated by unclassified and unclustered viral sequences. Furthermore, we predicted putative bacterial hosts for 211 vOTUs, with the majority of viruses predicted to infect a Proteobacteria (now Pseudomonadota) host. Overall, while limited, these results are consistent with the notion that both viruses and Cyanobacteria isolated from extreme environments are underrepresented in reference datasets. This work increases knowledge of viral diversity and sets a foundation for future exploration of viruses associated with terrestrial Cyanobacteria and their heterotroph associates, such as connecting specific viruses to critical cycling processes and investigating their metabolic functions.

microbiology↗

bioRxiv2019

Insights into the desert living skin microbiome: geography, soil depth, and crust type affect biocrust microbial communities and networks in Mojave Desert, USA

Biocrusts are the living skin of drylands, comprising diverse microbial communities that are essential to desert ecosystems. Although we have extensive knowledge on biocrust ecosystem function and what drives biodiversity in lichen and moss dominated biocrusts, much less is understood about the impacts of diversity among microbial communities. Moreover, most biocrust microbial composition studies have primarily focused on bacteria. We used amplicon-based metabarcode sequencing to explore composition of both fungal and bacterial communities in biocrusts. Specifically we tested how geography, soil depth, and crust type structured biocrust microbial communities or fungal-bacterial networks. Microbial communities were surveyed from biocrust surface and subsurface soils collected from Joshua Tree National Park, Granite Mountain, Kelso Dunes, and Cima volcanic flows located within the Mojave Desert, USA. Five biocrust types were examined: Light-algal, Cyano-lichen, Green-algal lichen, Smooth moss, and Rough moss crust types. We found the primary characteristics structuring biocrust microbial diversity were 1) geography, as central and southern Mojave sites displayed different community signatures, 2) presence of plant associated fungi (plant pathogens and wood saprotrophs), indicator, and endemic species were identified at each site, 3) soil depth patterns, as surface and subsurface microbial communities were distinctly structured, and 4) the crust type, which predicted distinct microbial compositions. Network analysis showed that Cyanobacteria and Dothideomycetes (Pleosporales) were the major hubs of overall biocrust microbial community. Such hierarchical spatial organization of biocrust communities and their associated biotic networks can have pronounced impacts to ecosystem functions. Our findings provide crucial insights for dryland restoration and sustainable management.

microbiology↗