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1. Closed circular genome sequence of a Microcystis aeruginosa PCC7806 Δ mcyB (UTK) non-toxic mutant

   https://doi.org/10.1128/MRA.00700-23  

   Stark, Gwendolyn F ; Truchon, Alexander R ; Dittmann, Elke ; Wilhelm, Steven W ( November 2023 , Microbiology Resource Announcements)

   Becket, Elinne (Ed.)

   Here we report the complete, closed genome of the non-toxicMicrocystis aeruginosaPCC7806 ΔmcyBmutant strain. This genome is 5,103,923 bp long, with a GC content of 42.07%. Compared to the published wild-type genome (Microcystis aeruginosaPCC7806SL), there is evidence of accumulated mutations beyond the inserted chloramphenicol resistance marker.

    

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2. The genetic and ecophysiological diversity of Microcystis

   https://doi.org/10.1111/1462-2920.15615  

   Dick, Gregory J. ; Duhaime, Melissa B. ; Evans, Jacob T. ; Errera, Reagan M. ; Godwin, Casey M. ; Kharbush, Jenan J. ; Nitschky, Helena S. ; Powers, McKenzie A. ; Vanderploeg, Henry A. ; Schmidt, Kathryn C. ; et al ( June 2021 , Environmental Microbiology)

   Microcystisis a cyanobacterium that forms toxic blooms in freshwater ecosystems around the world. Biological variation among taxa within the genus is apparent through genetic and phenotypic differences between strains and via the spatial and temporal distribution of strains in the environment, and this fine‐scale diversity exerts strong influence over bloom toxicity. Yet we do not know how varying traits ofMicrocystisstrains govern their environmental distribution, the tradeoffs and links between these traits, or how they are encoded at the genomic level. Here we synthesize current knowledge on the importance of diversity withinMicrocystisand on the genes and traits that likely underpin ecological differentiation of taxa. We briefly review spatial and environmental patterns ofMicrocystisdiversity in the field and genetic evidence for cohesive groups withinMicrocystis. We then compile data on strain‐level diversity regarding growth responses to environmental conditions and explore evidence for variation of community interactions acrossMicrocystisstrains. Potential links and tradeoffs between traits are identified and discussed. The resulting picture, while incomplete, highlights key knowledge gaps that need to be filled to enable new models for predicting strain‐level dynamics, which influence the development, toxicity and cosmopolitan nature ofMicrocystisblooms.

    

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3. Dual thermal ecotypes coexist within a nearly genetically identical population of the unicellular marine cyanobacterium Synechococcus

   https://doi.org/10.1073/pnas.2315701120  

   Kling, Joshua D. ; Lee, Michael D. ; Walworth, Nathan G. ; Webb, Eric A. ; Coelho, Jordan T. ; Wilburn, Paul ; Anderson, Stephanie I. ; Zhou, Qianqian ; Wang, Chunguang ; Phan, Megan D. ; et al ( November 2023 , Proceedings of the National Academy of Sciences)

   The extent and ecological significance of intraspecific functional diversity within marine microbial populations is still poorly understood, and it remains unclear if such strain-level microdiversity will affect fitness and persistence in a rapidly changing ocean environment. In this study, we cultured 11 sympatric strains of the ubiquitous marine picocyanobacteriumSynechococcusisolated from a Narragansett Bay (RI) phytoplankton community thermal selection experiment. Thermal performance curves revealed selection at cool and warm temperatures had subdivided the initial population into thermotypes with pronounced differences in maximum growth temperatures. Curiously, the genomes of all 11 isolates were almost identical (average nucleotide identities of >99.99%, with >99% of the genome aligning) and no differences in gene content or single nucleotide variants were associated with either cool or warm temperature phenotypes. Despite a very high level of genomic similarity, sequenced epigenomes for two strains showed differences in methylation on genes associated with photosynthesis. These corresponded to measured differences in photophysiology, suggesting a potential pathway for future mechanistic research into thermal microdiversity. Our study demonstrates that present-day marine microbial populations can harbor cryptic but environmentally relevant thermotypes which may increase their resilience to future rising temperatures.

    

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4. Phage Infection Restores PQS Signaling and Enhances Growth of a Pseudomonas aeruginosa lasI Quorum-Sensing Mutant

   https://doi.org/10.1128/jb.00557-21  

   Høyland-Kroghsbo, Nina Molin ; Bassler, Bonnie L. ( January 2022 , Journal of Bacteriology)

   Bondy-Denomy, Joseph (Ed.)

   ABSTRACT Chemical communication between bacteria and between bacteria and the bacteriophage (phage) viruses that prey on them can shape the outcomes of phage-bacterial encounters. Quorum sensing (QS) is a bacterial cell-to-cell communication process that promotes collective undertaking of group behaviors. QS relies on the production, release, accumulation, and detection of signal molecules called autoinducers. Phages can exploit QS-mediated communication to manipulate their hosts and maximize their own survival. In the opportunistic pathogen Pseudomonas aeruginosa , the LasI/R QS system induces the RhlI/R QS system, and in opposing manners, these two systems control the QS system that relies on the autoinducer called PQS. A P. aeruginosa Δ lasI mutant is impaired in PQS synthesis, leading to accumulation of the precursor molecule HHQ, and HHQ suppresses growth of the P. aeruginosa Δ lasI strain. We show that, in response to a phage infection, the P. aeruginosa Δ lasI mutant reactivates QS, which, in turn, restores pqsH expression, enabling conversion of HHQ into PQS. Moreover, downstream QS target genes encoding virulence factors are induced. Additionally, phage-infected P. aeruginosa Δ lasI cells transiently exhibit superior growth compared to uninfected cells. IMPORTANCE Clinical isolates of P. aeruginosa frequently harbor mutations in particular QS genes. Here, we show that infection by select temperate phages restores QS, a cell-to-cell communication mechanism in a P. aeruginosa QS mutant. Restoration of QS increases expression of genes encoding virulence factors. Thus, phage infection of select P. aeruginosa strains may increase bacterial pathogenicity, underscoring the importance of characterizing phage-host interactions in the context of bacterial mutants that are relevant in clinical settings. 

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5. Staphylococcus aureus lacking a functional MntABC manganese import system has increased resistance to copper

   https://doi.org/10.1111/mmi.14623  

   Al‐Tameemi, Hassan ; Beavers, William N. ; Norambuena, Javiera ; Skaar, Eric P. ; Boyd, Jeffrey M. ( October 2020 , Molecular Microbiology)

   S. aureusUSA300 isolates utilize thecopBLandcopAZgene products to prevent Cu intoxication. We created and examined a ΔcopAZΔcopBLmutant strain (cop‐). Thecop‐ strain was sensitive to Cu and accumulated intracellular Cu. We screened a transposon (Tn) mutant library in thecop‐ background and isolated strains with Tn insertions in themntABCoperon that permitted growth in the presence of Cu. The mutations were inmntAand they were recessive. Under the growth conditions utilized, MntABC functioned in manganese (Mn) import. When cultured with Cu, strains containing amntA::Tnaccumulated less Cu than the parent strain. Mn(II) supplementation improved growth whencop‐ was cultured with Cu and this phenotype was dependent upon the presence of MntR, which is a repressor ofmntABCtranscription. A ΔmntRstrain had an increased Cu load and decreased growth in the presence of Cu, which was abrogated by the introduction ofmntA::Tn. Over‐expression ofmntABCincreased cellular Cu load and sensitivity to Cu. The presence of amntA::Tnmutation protected iron‐sulfur (FeS) enzymes from inactivation by Cu. The data presented are consistent with a model wherein defective MntABC results in decreased cellular Cu accumulation and protection to FeS enzymes from Cu poisoning.

    

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