Heterotrophic Bacteria Dominate Catalase Expression during
            <i>Microcystis</i>
            Blooms

Smith, Derek J.; Berry, Michelle A.; Cory, Rose M.; Johengen, Thomas H.; Kling, George W.; Davis, Timothy W.; Dick, Gregory J.

doi:10.1128/aem.02544-21

Cited by 25 publications

(17 citation statements)

References 114 publications

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“…There was greatest phylogenetic conservation in the presence of genes for decomposition of reactive oxygen species (ROS), nitrogen (N) and phosphorous (P) metabolism, and carbon concentrating mechanisms (CCM). None of the WLE Microcystis isolates contained katG , an enzyme used for the degradation of hydrogen peroxide (Bernroitner et al, 2009); katG was previously shown to be absent from most, but not all cells, in natural WLE Microcystis populations (Smith et al, 2022a). However, t2prx , a type 2 peroxiredoxin (Schuurmans et al, 2018), was present in every strain analyzed.…”

Section: Resultsmentioning

confidence: 99%

“…In many cases, the associated bacteria were more abundant than the Microcystis strains present within each culture (Fig 5, Table S1), though biases in DNA extraction could influence this result. Associated bacterial genomes were also queried for catalase genes, which degrade hydrogen peroxide, thus ameliorating ROS stress on Microcystis (Morris et al, 2008; Smith et al, 2022a). Of the 22 cultures, 17 cultures contained organisms with catalase genes.…”

Section: Resultsmentioning

confidence: 99%

“…While katG , an enzyme used by cyanobacteria to degrade hydrogen peroxide (Bernroitner et al, 2009; Mutsuda et al, 1996), was undetected in all 21 Microcystis strains, a large portion of associated bacteria in these cultures contained catalase genes, suggesting they are likely important in alleviating ROS stress from the cyanoHAB phycosphere. During periods of rapid growth in WLE cyanoHABs, concentrations of hydrogen peroxide can reach high levels of 600-800 nM (Cory et al, 2016; Smith et al, 2022a), which can cause oxidative stress and cell death in microorganisms (Imlay, 2003; Latifi et al, 2009). Our results are consistent with previous studies suggesting “helper” heterotrophic bacteria are critical in facilitating rapid growth of cyanobacteria in aquatic systems (Morris et al, 2008; Smith et al, 2022a) by relieving ROS stress.…”

Section: Discussionmentioning

confidence: 99%

“…During periods of rapid growth in WLE cyanoHABs, concentrations of hydrogen peroxide can reach high levels of 600-800 nM (Cory et al, 2016; Smith et al, 2022a), which can cause oxidative stress and cell death in microorganisms (Imlay, 2003; Latifi et al, 2009). Our results are consistent with previous studies suggesting “helper” heterotrophic bacteria are critical in facilitating rapid growth of cyanobacteria in aquatic systems (Morris et al, 2008; Smith et al, 2022a) by relieving ROS stress.…”

Section: Discussionmentioning

confidence: 99%

“…Another dimension of Microcystis diversity is the microbiome of bacteria that are physically associated with Microcystis colonies. These microbiomes are Microcystis strain-specific (Smith et al, 2021) and likely engage in mutualistic interactions with Microcystis (Smith et al, 2022a, 2022b). While such interactions influence toxin production by other algae (Bates et al, 1995), the effects on toxin production by Microcystis are largely unknown.…”

Section: Introductionmentioning

confidence: 99%

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

Yancey

Denef

Errera

et al. 2022

Preprint

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Cyanobacteria harmful algal blooms (cyanoHABs) dominated byMicrocystisspp. 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 unialgalMicrocystiscultures 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 knownMicrocystisdiversity in natural populations. Only 5 isolates contained all the genes required for microcystin synthesis while 2 isolates contained a previously described partialmcyoperon. Microcystin production within cultures was also assessed using Enzyme-Linked Immunosorbent Assay (ELISA) and supported genomic results with high concentrations (up to 900 μg L-1) in cultures with completemcyoperons and no or low toxin detected otherwise. These xenic cultures also contained a substantial diversity of bacteria associated withMicrocystis, which has become increasingly recognized as an essential component of cyanoHAB community dynamics. These results highlight the genomic diversity amongMicrocystisstrains 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 relevantMicrocystisstrains from temperate North America, which is changing rapidly due to climate change.HighlightsTwenty one xenicMicrocystiscultures were isolated from western Lake Erie and capture the diversity ofMicrocystisstrains observed in natural populations as well as their associated bacteriaMicrocystisstrains show variability in core and accessory gene content, and genetically similar strains produce varying concentrations and congeners of microcystinsThis collection is a valuable resource for studying strain diversity and interactions betweenMicrocystisand associated bacteriaOur collection increases the availability of environmentally relevant strains from temperate North America, which is historically underrepresented in culture collections.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Yancey

Denef

Errera

et al. 2022

Preprint

Self Cite

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Variation in resource competition traits among Microcystis strains is affected by their microbiomes

Baker,

Godwin,

Khanam

et al. 2023

mLife

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Freshwater harmful algal blooms are often dominated by Microcystis, a phylogenetically cohesive group of cyanobacteria marked by extensive genetic and physiological diversity. We have previously shown that this genetic diversity and the presence of a microbiome of heterotrophic bacteria influences competitive interactions with eukaryotic phytoplankton. In this study, we sought to explain these observations by characterizing Monod equation parameters for resource usage (maximum growth rate μmax, half‐saturation value for growth Ks, and quota) as a function of N and P levels for four strains (NIES‐843, PCC 9701, PCC 7806 [WT], and PCC 7806 ΔmcyB) in presence and absence of a microbiome derived from Microcystis isolated from Lake Erie. Results indicated limited differences in maximum growth rates but more pronounced differences in half‐saturation values among Microcystis strains. The largest impact of the microbiome was reducing the minimal nitrogen concentration sustaining growth and reducing half saturation values, with variable results depending on the Microcystis strain. Microcystis strains also differed from each other in their N and P quotas and the extent to which microbiome presence affected them. Our data highlight the importance of the microbiome in altering Microcystis‐intrinsic traits, strain competitive hierarchies, and thus bloom dynamics. As quota, μmax, and Ks are commonly used in models for harmful algal blooms, our data suggest that model improvement may be possible by incorporating genotype dependencies of resource‐use parameters.

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