Biology subjects

Podowski, J. C.

Publications and source records attributed to Podowski, J. C..

3 recordsLinked to original sources

bioRxiv2025

Genomic reconstruction of Bacillus anthracis from complex environmental samples enables high throughput identification and lineage assignment in Pakistan

Bacillus anthracis, the causative agent of anthrax, is a highly virulent zoonotic pathogen primarily affecting domesticated and wild herbivores. Human exposure to B. anthracis is primarily through contact with infected animals or contaminated animal products. In Pakistan, where livestock vaccines are largely unavailable and infected carcasses are often disposed of improperly, the risk to humans, wildlife and livestock is significant. Currently, diagnosis of anthrax infections and outbreak tracing necessitates the isolation and culturing of B. anthracis, a process that requires BSL-3 facilities. In this study, we show that positive identification, genome reconstruction and lineage assignment can be accomplished using bioinformatic analysis of DNA extracted directly from environmental samples that would otherwise provide the starting material for isolation and culturing. This approach does not require laboratory target enrichment as is necessary for other pathogens, due in part to the extremely high bacterial load in the bloodstream in the deceased animals. Using these methods, we greatly expand the knowledge of endemic B. anthracis in Pakistan. We provide the first reference B. anthracis genomes from Pakistan since the 1970s and identify A.Br.014 Aust94 as a minor circulating sublineage alongside dominant A.Br.047 Vollum. Future work will focus on limits of detection and will determine if this bioinformatic method can be expanded more broadly for B. anthracis or other pathogens to replace typical culture-based methods.

bioinformatics↗

bioRxiv2023

Response of soil bacteria to PUREX chemicals suggests biomarker utility and bioremediation potential

Chemicals involved in plutonium uranium reduction extraction (PUREX) have the potential to be released from nuclear reprocessing facilities and accumulate in the environment. In order to understand how soil microbial communities respond to contamination by PUREX chemicals, we carried out a series of microcosm experiments, exposing chemically diverse soils to a range of concentrations of key chemicals used in the PUREX process. We tested 4 PUREX chemicals, and 5 soil types using 16S rRNA amplicon sequencing, determining that responses of microbial communities are dependent on the soil type in which they reside, and that tributyl phosphate exposure appears to generate the most reproducible and detectable shifts in microbial communities. We identified a number of key taxa that are consistently enriched in soils exposed to tributyl phosphate. These key taxa are either in the family Rhizobiaceae or genus Pseudomonas. The relative abundance of these key taxa is concentration dependent, and their abundance remains elevated at least 100 days post initial exposure. Using whole-shotgun metagenomic sequencing, we reconstructed the genomes of these key taxa and find a number of putative phosphotriesterase genes found only in Rhizobiaceae. We find the abundance of phosphotriesterase genes is significantly higher in samples exposed to tributyl phosphate. These phosphotriesterase genes, which degrade tributyl phosphate into dibutyl phosphate and butanol, may serve as effective biomarkers for tributyl phosphate contaminated soil, as well as a method for future bioremediation. ImportanceNuclear materials reprocessing facilities have the capacity to release toxic chemicals during normal operations or accidents. This study examines the ways in which chemicals involved with nuclear materials reprocessing impact microorganisms in the soil. Our intention was to understand the consequences of the release of these chemicals on ecosystems that may surround these reprocessing facilities. We find soil microbial communities change in response to some chemicals but not others, and that tributyl phosphate appears to generate the most reproducible and detectable shifts in microbial communities. Microorganisms in the family Rhizobiaceae increase in abundance in response to the addition of tributyl phosphate, and an examination of the genomes of these microbes suggest they may be able to break down tributyl phosphate to access the phosphosphate present in this chemical. Overall, this work demonstrates that changes in soil microbial communities in response to contamination with chemicals from nuclear materials reprocessing facilities may be predictable, and these responses could be leveraged to remediate contamination.

microbiology↗

bioRxiv2021

Large lakes harbor streamlined free-living nitrifiers

Microbial nitrification is a critical process governing nitrogen availability in aquatic systems. Freshwater nitrifiers have received little attention, leaving many unanswered questions about their taxonomic distribution, functional potential, and ecological interactions. Here, we reconstructed genomes to infer the metabolism and ecology of free-living picoplanktonic nitrifiers across the Laurentian Great Lakes, a connected series of five of Earths largest lakes. Surprisingly, ammonia oxidizing Bacteria (AOB) related to Nitrosospira dominated over ammonia oxidizing Archaea (AOA) at nearly all stations, with distinct ecotypes prevailing in the transparent, oligotrophic upper lakes compared to Lakes Erie and Ontario. Unexpectedly, one ecotype of Nitrosospira encodes proteorhodopsin, which could enhance survival in conditions where ammonia oxidation is inhibited or substrate limited. Nitrite oxidizing Bacteria (NOB) Ca. Nitrotoga and Nitrospira fluctuated in dominance, with the latter prevailing in deeper, less productive basins. Genome reconstructions reveal highly reduced genomes and features consistent with genome streamlining, along with diverse adaptations to sunlight and oxidative stress and widespread capacity for organic nitrogen use. Our findings expand the known functional diversity of nitrifiers and establish their ecological genomics in large lake ecosystems. By elucidating links between microbial biodiversity and biogeochemical cycling, our work also informs ecosystem models of the Laurentian Great Lakes, a critical freshwater resource experiencing rapid environmental change. ImportanceMicroorganisms play critical roles in Earths nitrogen cycle. In lakes, microorganisms called nitrifiers derive energy from reduced nitrogen compounds. In doing so, they transform nitrogen into a form that can ultimately be lost to the atmosphere by a process called denitrification, which helps mitigate nitrogen pollution from fertilizer runoff and sewage. Despite their importance, freshwater nitrifiers are virtually unexplored. To understand their diversity and function, we reconstructed genomes of freshwater nitrifiers across some of Earths largest freshwater lakes, the Laurentian Great Lakes. We discovered several new species of nitrifiers specialized for clear low nutrient waters, and distinct species in comparatively turbid Lake Erie. Surprisingly, one species may be able to harness light energy using a protein called proteorhodopsin, despite the fact that nitrifiers typically live in deep dark water. Our work reveals unique biodiversity of the Great Lakes and fills key gaps in our knowledge of an important microbial group, the nitrifiers.

microbiology↗