More Like this

1. Rival phytoplankton contribute to the cross protection of Prochlorococcus from oxidative stress

   https://doi.org/10.1128/aem.01128-24  

   Calfee, Benjamin C; Bowden, Emily C; Zinser, Erik R (May 2025, Applied and Environmental Microbiology)

   Bose, Arpita (Ed.)

   ABSTRACT The marine cyanobacteriumProchlorococcusnumerically dominates the phytoplankton communities in all lower latitude, open ocean environments. Having lost the catalase gene,Prochlorococcusis highly susceptible to exogenous hydrogen peroxide (H₂O₂) produced at the ocean’s surface. Protection by H₂O₂-scavenging heterotrophic “helper” bacteria has been demonstrated in laboratory cultures and implicated as an important mechanism ofProchlorococcussurvival in the ocean. Importantly, some other phytoplankton can also scavenge H₂O₂, suggesting these competing microbes may inadvertently protectProchlorococcus. In this study, we assessed the ability of co-occurring phytoplankton, the cyanobacteriumSynechococcusand picoeukaryotesMicromonasandOstreococcus, to protectProchlorococcusfrom H₂O₂exposure when cocultured at ecologically relevant abundances. All three genera could significantly degrade H₂O₂and diminishProchlorococcusmortality during H₂O₂exposures simulating photochemical production and rainfall events. We suggest that these phytoplankton groups contribute significantly to the H₂O₂microbial sink of the open ocean, thus complicating their relationships with and perhaps contributing to the evolutionary history ofProchlorococcus.IMPORTANCEThe marine cyanobacteriumProchlorococcusis the most abundant photosynthetic organism on the planet and is crucially involved in microbial community dynamics and biogeochemical cycling in most tropical and subtropical ocean waters. This success is due, in part, to the detoxification of the reactive oxygen species hydrogen peroxide (H₂O₂) performed by “helper” organisms. Earlier work identified heterotrophic bacteria as helpers, and here, we demonstrate that rival cyanobacteria and picoeukaryotic phytoplankton can also contribute to the survival ofProchlorococcusduring exposure to H₂O₂. Whereas heterotrophic bacteria helper organisms can benefit directly from promoting the survival of carbon-fixingProchlorococcuscells, phytoplankton helpers may suffer a twofold injury: production of H₂O₂degrading enzymes constrains already limited resources in oligotrophic environments, and the activity of these enzymes bolsters the abundance of their numerically dominant competitor. These findings build toward a better understanding of the intricate dynamics and interactions that shape microbial community structure in the open ocean. 

   more » « less
2. Toxicity of azoles towards the anaerobic ammonium oxidation (anammox) process

   https://doi.org/10.1002/jctb.6285  

   Lakhey, Nivrutti; Li, Guangbin; Sierra‐Alvarez, Reyes; Field, Jim_A (December 2019, Journal of Chemical Technology & Biotechnology)

   Abstract BACKGROUNDAzoles are an important class of compounds that are widely used as corrosion inhibitors in aircraft de‐icing agents, cooling towers, semiconductor manufacturing and household dishwashing detergents. They also are important moieties in pharmaceutical drugs and fungicides. Azoles are widespread emerging contaminants occurring frequently in water bodies. Azole compounds can potentially cause inhibition towards key biological processes in natural ecosystems and wastewater treatment processes. Of particular concern is the inhibition of azoles to the nitrification process (aerobic oxidation of ammonium). This study investigated the acute toxicity of azole compounds towards the anaerobic ammonia oxidation (anammox) process, which is an important environmental biotechnology gaining traction for nutrient‐nitrogen removal during wastewater treatment. In this study, using batch bioassay techniques, the anammox toxicity of eight commonly occurring azole compounds was evaluated. RESULTSThe results show that 1H‐benzotriazole and 5‐methyl‐1H‐benzotriazole had the highest inhibitory effect on the anammox process, causing 50% decrease in anammox activity (IC₅₀) at concentrations of 19.6 and 17.8 mg L⁻¹, respectively. 1H‐imidazole caused less severe toxicity with an IC₅₀of 79.4 mg L⁻¹. The other azole compounds were either nontoxic (1H‐pyrazole, 1H‐1,2,4‐triazole and 1‐methyl‐pyrazole) or at best mildly toxic (1H‐benzotriazole‐5‐carboxylic acid and 3,5‐dimethyl‐1H‐pyrazole) towards the anammox bacteria at the concentrations tested. CONCLUSIONSThis study showed that most azole compounds tested displayed mild to low or no toxicity towards the anammox bacteria. The anammox bacteria were found to be far less sensitive to azoles compared to nitrifying bacteria. © 2019 Society of Chemical Industry 

   more » « less
3. ROS are evolutionary conserved cell-to-cell stress signals

   https://doi.org/10.1073/pnas.2305496120  

   Fichman, Yosef; Rowland, Linda; Oliver, Melvin J; Mittler, Ron (August 2023, Proceedings of the National Academy of Sciences)

   Cell-to-cell communication is fundamental to multicellular organisms and unicellular organisms living in a microbiome. It is thought to have evolved as a stress- or quorum-sensing mechanism in unicellular organisms. A unique cell-to-cell communication mechanism that uses reactive oxygen species (ROS) as a signal (termed the “ROS wave”) was identified in flowering plants. This process is essential for systemic signaling and plant acclimation to stress and can spread from a small group of cells to the entire plant within minutes. Whether a similar signaling process is found in other organisms is however unknown. Here, we report that the ROS wave can be found in unicellular algae, amoeba, ferns, mosses, mammalian cells, and isolated hearts. We further show that this process can be triggered in unicellular and multicellular organisms by a local stress or H₂O₂treatment and blocked by the application of catalase or NADPH oxidase inhibitors and that in unicellular algae it communicates important stress–response signals between cells. Taken together, our findings suggest that an active process of cell-to-cell ROS signaling, like the ROS wave, evolved before unicellular and multicellular organisms diverged. This mechanism could have communicated an environmental stress signal between cells and coordinated the acclimation response of many different cells living in a community. The finding of a signaling process, like the ROS wave, in mammalian cells further contributes to our understanding of different diseases and could impact the development of drugs that target for example cancer or heart disease. 

   more » « less
4. Ligand and Linkage Isomers of Bis(ethylthiocarbamato) Copper Complexes with Cyclic C ₆ H ₈ Backbone Substituents: Synthesis, Characterization, and Antiproliferation Activity

   https://doi.org/10.1002/ejic.202300447  

   Bajaj, Kritika; Andres, Sarah_A; Hofsommer, Dillon_T; Chekwube_Michael, Okolocha; Mashuta, Mark_S; Bates, Paula_J; Buchanan, Robert_M; Grapperhaus, Craig_A (September 2023, European Journal of Inorganic Chemistry)

   Abstract A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3‐methylpentyl (H₂L²) and cyclohexyl (H₂L³) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL^2a/3ahave two imino N and two S donors resulting in three five‐member chelate rings (555 isomers). The kinetic isomers CuL^2b/3bhave one imino and one hydrazino N donor and two S donors resulting in four‐, six‐, and five‐member rings (465 isomers). The 555 isomers have more accessible Cu^II/Ipotentials (E_1/2=−811/−768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E_1/2=−923/‐854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR‐90) using the MTT assay. CuL^2awas potent (^A549EC₅₀=0.080 μM) and selective (^IMR‐90EC₅₀/^A549EC₅₀=25) for A549. Its linkage isomer CuL^2bhad equivalent A549 activity, but lower selectivity (^IMR‐90EC₅₀/^A549EC₅₀=12.5). The isomers CuL^3aand CuL^3bwere less potent with^A549EC₅₀ values of 1.9 and 0.19 M and less selective with^IMR‐90EC₅₀/^A549EC₅₀ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity. 

   more » « less
5. Uptake of Phytoplankton-Derived Carbon and Cobalamins by Novel Acidobacteria Genera in Microcystis Blooms Inferred from Metagenomic and Metatranscriptomic Evidence

   https://doi.org/10.1128/aem.01803-21  

   Smith, Derek J.; Kharbush, Jenan J.; Kersten, Roland D.; Dick, Gregory J. (July 2022, Applied and Environmental Microbiology)

   Glass, Jennifer B. (Ed.)

   ABSTRACT Interactions between bacteria and phytoplankton can influence primary production, community composition, and algal bloom development. However, these interactions are poorly described for many consortia, particularly for freshwater bloom-forming cyanobacteria. Here, we assessed the gene content and expression of two uncultivated Acidobacteria from Lake Erie Microcystis blooms. These organisms were targeted because they were previously identified as important catalase producers in Microcystis blooms, suggesting that they protect Microcystis from H 2 O 2 . Metatranscriptomics revealed that both Acidobacteria transcribed genes for uptake of organic compounds that are known cyanobacterial products and exudates, including lactate, glycolate, amino acids, peptides, and cobalamins. Expressed genes for amino acid metabolism and peptide transport and degradation suggest that use of amino acids and peptides by Acidobacteria may regenerate nitrogen for cyanobacteria and other organisms. The Acidobacteria genomes lacked genes for biosynthesis of cobalamins but expressed genes for its transport and remodeling. This indicates that the Acidobacteria obtained cobalamins externally, potentially from Microcystis , which has a complete gene repertoire for pseudocobalamin biosynthesis; expressed them in field samples; and produced pseudocobalamin in axenic culture. Both Acidobacteria were detected in Microcystis blooms worldwide. Together, the data support the hypotheses that uncultured and previously unidentified Acidobacteria taxa exchange metabolites with phytoplankton during harmful cyanobacterial blooms and influence nitrogen available to phytoplankton. Thus, novel Acidobacteria may play a role in cyanobacterial physiology and bloom development. IMPORTANCE Interactions between heterotrophic bacteria and phytoplankton influence competition and successions between phytoplankton taxa, thereby influencing ecosystem-wide processes such as carbon cycling and algal bloom development. The cyanobacterium Microcystis forms harmful blooms in freshwaters worldwide and grows in buoyant colonies that harbor other bacteria in their phycospheres. Bacteria in the phycosphere and in the surrounding community likely influence Microcystis physiology and ecology and thus the development of freshwater harmful cyanobacterial blooms. However, the impacts and mechanisms of interaction between bacteria and Microcystis are not fully understood. This study explores the mechanisms of interaction between Microcystis and uncultured members of its phycosphere in situ with population genome resolution to investigate the cooccurrence of Microcystis and freshwater Acidobacteria in blooms worldwide. 

   more » « less