Two DevBCA‐like ABC transporters are involved in the multidrug resistance of the cyanobacterium Anabaena sp. PCC 7120

Response and acclimation of cyanobacteria to acidification: A comprehensive review

Cyanobacteria, as vital components of aquatic ecosystems, face increasing challenges due to acidification driven by various anthropogenic and natural factors. Understanding how cyanobacteria adapt and respond to acidification is crucial for predicting their ecological dynamics and potential impacts on ecosystem health. This comprehensive review synthesizes current knowledge on the acclimation mechanisms and responses of cyanobacteria to acidification stress. Detailly, ecological roles of cyanobacteria were firstly briefly concluded, followed by the effects of acidification on aquatic ecosystems and cyanobacteria. Then the review focuses on the physiological, biochemical, and molecular strategies employed by cyanobacteria to cope with acidification stress, highlighting key adaptive mechanisms and their ecological implications. Finally, a summary of strategies to enhance acid resistance in cyanobacteria and future directions was discussed. Utilizing omics data and machine learning technology to build a cyanobacterial acid regulatory network allows for predicting the impact of acidification on cyanobacteria and inferring its broader effects on ecosystems. Additionally, acquiring acid-tolerant chassis cells of cyanobacteria through innovative techniques facilitates the advancement of environmentally friendly production of acidic chemicals. By synthesizing empirical evidence and theoretical frameworks, this review aims to elucidate the complex interplay between cyanobacteria and acidification stressors, providing insights for future research directions and ecosystem management strategies.

Investigation of the antimicrobial susceptibility patterns of marine cyanobacteria in Bohai Bay: Cyanobacteria may be important hosts of antibiotic resistance genes in marine environment

Marine cyanobacteria, as widely distributed and photosynthetically autotrophic bacteria in the ocean, may contribute to the global dissemination of antibiotic resistance genes (ARGs) and develop a different antimicrobial susceptibility pattern from heterotrophic bacteria and cyanobacteria from freshwater environments. However, studies on antimicrobial susceptibility and the carriage of ARGs in marine cyanobacteria are still very limited. In this study, the antibiotic resistance characteristics of cyanobacteria in nearshore waters were examined through field monitoring and laboratory investigations, which included PCR detection and ARG transformation. The results showed a positive correlation between marine cyanobacteria and some ARGs in the nearshore waters of Bohai Bay. Moreover, most screened cyanobacteria showed high minimum inhibitory concentration (MIC) values for polymyxins, tetracyclines, kanamycin, and sulfonamides, moderate MIC values for streptomycin, chloramphenicol, rifampicin, and norfloxacin, and low MIC values for roxithromycin and cephalosporins. The blaTEM, blaKPC, sul1, sul2, strA, tetA, tetB, tetC, tetM, mdfA, and intI1 genes were detected in the screened marine cyanobacteria. The highest detection rates were observed for blaTEM (93.3 %), sul1 (56.6 %), sul2 (90 %), and strA (73.3 %). The detection rate of tetA (33.3 %) was the highest among the tetracycline resistance genes, and mdfA, a multidrug-resistant pump gene with resistance to tetracycline, also showed a high detection level (23.3 %). Overall, most of the screened marine cyanobacteria were found to tolerate multiple antibiotics in seawater, and the condition of the ARGs carriage was serious. Furthermore, the screened marine Synechocystis sp. C12-2 demonstrated the ability to accept ARGs on the RP4 plasmid through natural transformation and showed reduced sensitivity to ampicillin, suggesting the possibility that some marine cyanobacteria could acquire ARGs from the environment through horizontal gene transfer. Thus, marine cyanobacteria may play an important role in the propagation of marine ARGs.

An Insight into the Exploration of Antibiotic Resistance Genes in Calorie Restricted Diet Fed Mice

Antibiotic resistance genes (ARGs) threaten the success of modern drugs against multidrug resistant infections. ARGs can be transferred to opportunistic pathogens by horizontal gene transfer (HGT). Many studies have investigated the characteristics of ARGs in various chemical stressors. Studies on the effects of dietary nutrition and dietary patterns on ARGs are rare. The study first demonstrated the effect of calorie restricted (CR) diet on the ARGs and mobile genetic elements (MGEs) in mouse feces and explored their relationship with gut microbiota and their functions. The results showed that the abundance of the total ARGs in mouse feces of the CR group increased, especially tetracycline ARGs (tetW-01). The abundance of the MLSB ARGs (ermB) decreased evidently in mouse feces of the CR group. In addition, the total abundance of MGEs decreased evidently in the CR group, especially tnpA-03. In the meantime, the abundance of Lactobacillus and Bifidobacterium in mouse feces of the CR group increased remarkably. The Spearman correlation analysis between gut microbiota and ARGs showed that several probiotics were significantly positively correlated with ARGs (tetW-01), which might be the main contribution to the increase in ARGs of the CR group.

Quantitative Proteomics at Early Stages of the Symbiotic Interaction Between Oryza sativa and Nostoc punctiforme Reveals Novel Proteins Involved in the Symbiotic Crosstalk

Symbiosis between cyanobacteria and plants is considered pivotal for biological nitrogen deposition in terrestrial ecosystems. Despite extensive knowledge of the ecology of plant-cyanobacterium symbioses, little is known about the molecular mechanisms involved in recognition between partners. Here, we conducted a quantitative sequential window acquisition of all theoretical fragment ion spectra mass spectrometry pipeline to analyze protein changes in Oryza sativa and Nostoc punctiforme during early events of symbiosis. We found differentially expressed proteins in both organisms linked to several biological functions, including signal transduction, adhesion, defense-related proteins and cell wall modification. In N. punctiforme we found increased expression of 62 proteins that have been previously described in other Nostoc-plant symbioses, reinforcing the robustness of our study. Our findings reveal new proteins activated in the early stages of the Nostoc-Oryza symbiosis that might be important for the recognition between the plant and the host. Oryza mutants in genes in the common symbiosis signaling pathway (CSSP) show reduced colonization efficiency, providing first insights on the involvement of the CSSP for the accommodation of N. punctiforme inside the plant cells. This information may have long-term implications for a greater understanding of the symbiotic interaction between Nostoc and land plants.

Structure, Assembly, and Function of Tripartite Efflux and Type 1 Secretion Systems in Gram-Negative Bacteria

Tripartite efflux pumps and the related type 1 secretion systems (T1SSs) in Gram-negative organisms are diverse in function, energization, and structural organization. They form continuous conduits spanning both the inner and the outer membrane and are composed of three principal components-the energized inner membrane transporters (belonging to ABC, RND, and MFS families), the outer membrane factor channel-like proteins, and linking the two, the periplasmic adaptor proteins (PAPs), also known as the membrane fusion proteins (MFPs). In this review we summarize the recent advances in understanding of structural biology, function, and regulation of these systems, highlighting the previously undescribed role of PAPs in providing a common architectural scaffold across diverse families of transporters. Despite being built from a limited number of basic structural domains, these complexes present a staggering variety of architectures. While key insights have been derived from the RND transporter systems, a closer inspection of the operation and structural organization of different tripartite systems reveals unexpected analogies between them, including those formed around MFS- and ATP-driven transporters, suggesting that they operate around basic common principles. Based on that we are proposing a new integrated model of PAP-mediated communication within the conformational cycling of tripartite systems, which could be expanded to other types of assemblies.

The HlyD-like membrane fusion protein All5304 is essential for acid stress survival of the filamentous cyanobacterium Anabaena sp. PCC 7120

Acid stress is an environmental problem for plants and fresh water cyanobacteria like the filamentous, heterocyst forming species Anabaena sp. PCC 7120 (hereafter Anabaena sp.). Heterocyst differentiation, cell-cell communication and nitrogen fixation has been deeply studied in this model organism, but little is known about the cellular response of Anabaena sp. to decreased pH values, causing acid stress. ATP-binding cassette (ABC) transporters are involved in acid stress response in other bacteria, by exporting proteins responsible for survival under acidification. The genome of Anabaena sp. encodes numerous ABC transporter components, whose function is not known yet. Here, we describe the function of the gene all5304 encoding a protein with homology to membrane fusion proteins of tripartite efflux pumps driven by ABC transporters like HlyBD-TolC of Escherichia coli. The all5304 mutant shows less resistance against low pH, even though the expression of the gene is independent from the pH of the medium. We compared the exoproteome of the wild type and mutant cultures and identified three proteins-candidate substrates of the putative transporter. Including the in silico analysis of All5304, our results suggest that All5304 functions as part of an efflux pump, secreting of a protein necessary for acid tolerance in Anabaena sp.