Biology subjects

Virta, M.

Publications and source records attributed to Virta, M..

4 recordsLinked to original sources

bioRxiv2026

Antibiotic Resistomes And Microbial Communities In The 18th-Century Urban Settlement And Slaughterhouse Environment

Antimicrobial resistance (AMR) is an ancient and natural phenomenon, yet it now poses a critical threat to global health. Human activities, particularly animal husbandry, have shaped microbial evolution by creating manure-rich environments that promote interactions between environmental and host-associated bacteria and facilitate horizontal gene transfer. Here, we investigated dormant, potential antibiotic-producing bacteria, microbial communities, and their AMR genes and mobile genetic elements in 18th-century preindustrial slaughterhouse surroundings excavated in Turku, Finland. By combining cultivation, genomic analyses, metagenomic sequencing, and ancient DNA authentication methods, we reconstructed preindustrial microbiomes and resistomes to better understand the early ecology and evolution of AMR, and to explore the role of antibiotic-producing bacteria in the emergence of AMR. Our results reveal putative ancestral forms of resistance mechanisms only recently characterized, such as fosfomycin thiol transferase fosI, plasmid-associated tmexCD-toprJ efflux pumps conferring resistance to last-resource antibiotic tigecycline, as well as sequences related to mobility of AMR genes. These findings demonstrate that key AMR elements were already present prior to widespread antibiotic use, reflecting their long-term environmental origins.

microbiology↗

bioRxiv2026

Bio-based fertilizers shape soil microbiome, resistome and mobilome through metabolism of antibiotic-producing Streptomyces

Streptomyces are abundant soil inhabitants with extensive secondary metabolism and antibiotic resistance traits. Yet, their ecological role in shaping soil antibiotic resistome dynamics remains understudied. Here, we investigated how two different bio-based fertilizers harbouring Streptomyces shaped soil resistome and mobilome by combining genome analysis of eight Streptomyces isolates to metagenomic profiling of soils before fertilization, within 48 hours after fertilizer application, and six weeks after. Streptomyces genomes showed linkages among antibiotic resistance genes, carbohydrate-active enzymes, and antibiotic-production-associated biosynthetic gene clusters, connecting resistance and biosynthesis to broader metabolic strategies. Relationships between carbon degradation and biosynthesis associated with specific enzyme families, indicating that carbon availability shapes secondary metabolism. We confirmed experimentally that antibacterial potential varied with carbon source, suggesting that microbial activity during manufacturing of the bio-based fertilizers may create localized selection pressures before fertilizers enter the soil. Fertilization with the studied materials induced modest but consistent shifts in resistome and mobilome without major changes in dominant taxa or overall bacterial abundances, indicating functional reorganization within soil communities. Diversity of antibiotic resistance genes and mobile genetic elements increased, whereas abundance changes were small. Mobile genetic element composition showed stronger responses that were associated with fertilizer inputs, Streptomyces abundance, and taxa linked to faecal and resistance sources. Together, our results show that bio-based fertilizers shape soil resistome primarily through ecological restructuring of resident soil communities, while carbon-dependent microbial activity within fertilizers may enrich resistance. These factors should be considered in manufacturing of bio-based fertilizer as well as in designing agricultural practices.

microbiology↗

bioRxiv2025

Sulfonamide resistance gene sul4 is hosted by common wastewater sludge bacteria and found in various newly described contexts and hosts including clinically relevant species

The introduction of the first broad-spectrum antibiotics, sulfonamide drugs fundamentally revolutionized medicine in the 1930s. Shortly after and ever since sulfonamide resistance genes (sul genes) have been widely detected. Still, the most recent variant of these genes sul4, was first described only in 2017 and its host range and transmission mechanisms are still largely unknown. Here we applied PacBio long-read metagenomic sequencing and bacterial methylation signals to investigate the genetic contexts and bacterial carriage of the sul4 gene in wastewater. Furthermore, we extended our description of sul4 carriers to previously published data sets. Our results indicate that sul4 is prominently found in sludge and hosted by various bacteria such as the species from the phyla Myxococcota and Chloroflexota and genera Trichlorobacter, and Desulfobacillus, which are commonly found in activated sludge. Additionally, according to our results, sul4 has already spread into multiple strains of opportunistic human pathogens, such as Aeromonas and Moraxella in addition to the previously described Salmonella. The sequence region flanking sul4 included a truncated folK gene, and an ISCR28-element, and exhibited a high degree of conservation across the investigated sequences. Furthermore, the module was associated with various integron integrase genes. Also, other mobility-related elements that could further increase the likelihood of sul4 mobilization were detected. Altogether, our results describing the sul4 hosts of bacteria from distant lineages indicate the efficient mobility of sul4 by genetic elements that traverse both clinical and environmental bacteria. Finally, we suggest that wastewater may provide favorable conditions for such horizontal gene transfer events. ImportanceAntibiotic resistance is an ancient phenomenon and a common trait for many environmental bacteria. However, human activities in the post-antibiotic era, coupled with the bacterias ability to exchange genetic material across different lineages, have drastically increased the spread of resistance traits among bacteria from various niches. The primary concern is the resistance genes encoded by infections causing pathogens, already causing over one million deaths annually and indirectly contributing to nearly four million more. Therefore, understanding the bacteria that harbor ARGs and the genetic mechanisms driving their mobilization is crucial for understanding the dynamics and emerging trends of resistance. Here, we focus on revealing these crucial aspects of the newly discovered sulfonamide resistance gene sul4. Given the limitations of the metagenomic approach in linking the functional genes to their host genomes, the significance of our research lies in our workflow that allows this linkage by identification of shared methylation profiles.

microbiology↗

bioRxiv2019

Formula alters preterm infant gut microbiota and increases its antibiotic resistance load

Infants are at a high risk of acquiring infections caused by antibiotic resistant bacterial strains. Antibiotic resistance gene (ARG) load is typically higher in newborns than in adults, but it is unknown which factors besides antibiotic treatment affect the load. Our study demonstrates that inclusion of any formula in the newborn diet causes shifts in microbial community composition that result in higher ARG loads in formula-fed infants compared to infants not fed formula. The effect of formula was especially strong in premature newborns and newborns treated with antibiotics. Interestingly, antibiotics alone without formula did not have a detectable impact on the ARG load of the newborn gut. We also observed that formula-fed infants had enriched numbers of pathogenic species and were depleted in typical infant gut species such as Bifidobacterium bifidum. The results suggest infant feeding choices should include assessment of risks associated with elevated ARG abundance.

microbiology↗