Biology subjects

Kiledal, E. A.

Publications and source records attributed to Kiledal, E. A..

4 recordsLinked to original sources

bioRxiv2024

Metagenomic Insights into the Spatio-temporal Variation of Metal and Antibiotic Resistance Genes in Lake Erie

Antibiotic resistance and metal toxicity in freshwater bodies have human health impacts and carry economic implications worldwide. The presence of metal and antibiotic resistance genes within microbial communities can be informative about both issues. The Laurentian Great Lakes contain nearly 20% of the worlds supply of freshwater; however, it is unclear how these genes are changing over time in this system. In this study, we characterized these genes in nearly two hundred metagenomes collected from multiple sites in western Lake Erie at a five-year time interval: 2014-2019. 11 metal resistance genes (MRGs) and nine antibiotic resistance genes (ARGs) were characterized and demonstrated significant changes in diversity and spatial distribution. Increased abundance was observed for genes like aac(3) and TEM-1B conferring resistance to aminoglycoside (gentamicin) and {beta}-lactam antibiotics, respectively. MRGs associated with mercury, lead, and arsenic also increased in abundance over the five years. Collectively, our data point to a notable increase in both ARGs and MRGs in Lake Erie over five years, with a specific and significant increase in the abundance of genes conferring resistance to aminoglycoside and {beta}-lactam antibiotic resistance and mercury contamination. Future integrated and systematic freshwater microbiome and public health investigations are needed to assess the potential impact on humans and environmental health from increasing microbial antibiotic and metal resistance in large freshwater reservoirs like the Great Lakes. IMPORTANCEAntibiotic and metal resistance genes (ARGs and MRGs) in microbial communities of the Laurentian Great Lakes have significant human and environmental health implications. However, an assessment of the Great Lakes microbiome for ARGs and MRGs is lacking. The abundance of 11 MRGs and 9 ARGs was characterized between 2014 and 2019 and showed significant abundance differences. Specifically, we observed an increase in genes conferring resistance to aminoglycoside (gentamicin) and {beta}-lactam antibiotics (amongst the most commonly utilized antibiotics in humans), such as aac(3) and TEM-1B, respectively. MRGs conferring resistance to mercury, lead, and arsenic also increased in abundance, with the largest increase observed for mercury resistance genes such as MerA, MerP, and MerT. Collectively, these findings point to a concerning increased abundance of both ARGs and MRGs in Lake Erie. Further studies to assess the causes for the increase and the direct impact on human and environmental health are needed.

microbiology↗

bioRxiv2023

THE DUAL ROLE OF THE MICROCYSTIS AERUGINOSA MICROBIOME ON CYANOTOXIN PRODUCTION: COMPETITION FOR AND REMINERALIZATION OF ORGANIC NITROGEN

Nutrient-induced blooms of the globally abundant freshwater toxic cyanobacterium Microcystis are the cause of worldwide public and ecosystem health concerns. The response of Microcystis growth and toxin production to new and recycled nitrogen (N) inputs, and the impact of heterotrophic bacteria in the Microcystis phycosphere on these processes are not well understood. Here, using microbiome transplant experiments, cyanotoxin analysis, and stable isotope tracing to measure N incorporation and exchange at single cell resolution, we monitored the growth, cyanotoxin production, and microbiome community structure of several Microcystis strains grown on amino acids and proteins as the sole N source. We demonstrate that 1) organic N availability shapes the microbiome community structure in the Microcystis phycosphere; 2) external organic N input leads to lower bacterial colonization of the phycosphere; 3) certain Microcystis strains can directly uptake amino acids, but with lower rates than heterotrophic bacteria; 4) biomass-specific microcystin production is not impacted by N source (i.e., nitrate, amino acids and protein) but rather by total N availability; and 5) some bacterial communities compete with Microcystis for organic N, but others remineralize organic N, in the process producing bio-available N for Microcystis. We conclude that organic N input can support Microcystis blooms and toxin production, and Microcystis-associated microbial communities play critical roles by influencing cyanobacterial succession through either decreasing (via competition) or increasing (via remineralization) N availability, especially under inorganic N scarcity.

microbiology↗

bioRxiv2022

The Western Lake Erie Culture Collection: A promising resource for evaluating the physiological and genetic diversity of Microcystis and its associated microbiome

Cyanobacteria harmful algal blooms (cyanoHABs) dominated by Microcystis spp. have significant public health and economic implications in freshwater bodies around the world. These blooms are capable of producing a variety of cyanotoxins, including microcystins, that affect fishing and tourism industries, human and environmental health, and access to drinking water. In this study, we isolated and sequenced the genomes of 21 unialgal Microcystis cultures collected from western Lake Erie between 2017-2019. While some cultures isolated in different years have a high degree of genetic similarity (Average Nucleotide Identity >99%), genomic data shows that these cultures also represent much of the breadth of known Microcystis diversity in natural populations. Only 5 isolates contained all the genes required for microcystin synthesis while 2 isolates contained a previously described partial mcy operon. Microcystin production within cultures was also assessed using Enzyme-Linked Immunosorbent Assay (ELISA) and supported genomic results with high concentrations (up to 900 g L-1) in cultures with complete mcy operons and no or low toxin detected otherwise. These xenic cultures also contained a substantial diversity of bacteria associated with Microcystis, which has become increasingly recognized as an essential component of cyanoHAB community dynamics. These results highlight the genomic diversity among Microcystis strains and associated bacteria in Lake Erie, and their potential impacts on bloom development, toxin production, and toxin degradation. This collection significantly increases the availability of environmentally relevant Microcystis strains from temperate North America, which is changing rapidly due to climate change. HighlightsO_LITwenty one xenic Microcystis cultures were isolated from western Lake Erie and capture the diversity of Microcystis strains observed in natural populations as well as their associated bacteria C_LIO_LIMicrocystis strains show variability in core and accessory gene content, and genetically similar strains produce varying concentrations and congeners of microcystins C_LIO_LIThis collection is a valuable resource for studying strain diversity and interactions between Microcystis and associated bacteria C_LIO_LIOur collection increases the availability of environmentally relevant strains from temperate North America, which is historically underrepresented in culture collections. C_LI

microbiology↗

bioRxiv2022

Metagenomic analysis of concrete bridge reveals a microbial community dominated by halophilic Bacteria and Archaea

Concrete hosts a small but diverse microbiome that changes over time. Shotgun metagenomic sequencing would enable assessment of both diversity and function of the microbial community in concrete, but because the biomass in concrete is so low, this analysis is highly affected by laboratory contamination. Here, we demonstrate improved DNA extraction from concrete, and show that this method provides DNA of sufficient quality and quantity to do shotgun metagenomic sequencing. DNA was extracted from a sample of concrete obtained from a road bridge and sequenced with Illumina MiSeq. This microbial community was dominated by halophilic Bacteria and Archaea, with enriched functional pathways related to osmotic stress responses. Prior work found that halophilic bacteria were relatively rare in younger concrete samples, which had abundant oligotrophic taxa. These results suggest that as concrete ages and weathers, salt and osmotic stresses become more important selective pressures, and suggest that long-term persistence and performance of microbes for biorepair or biosensing applications might improve if halophilic strains were used.

microbiology↗