As major players in open-water marine food webs, protist plankton are indispensable. Despite the traditional separation of phototrophic phytoplankton and phagotrophic zooplankton, recent research highlights that many organisms exhibit a combination of phototrophy and phagotrophy within their single cells, thereby defining a new category known as mixoplankton. According to the mixoplankton theory, phytoplankton (specifically diatoms) are incapable of phagotrophy, a contrasting characteristic to zooplankton, which are incapable of phototrophy. This revision reconfigures marine food webs, moving from localized to worldwide perspectives. We introduce the first comprehensive database dedicated to marine mixoplankton, collecting existing data on species identification, allometric growth, physiological adaptations, and their interconnectedness within the food chain. The Mixoplankton Database (MDB) will furnish researchers overcoming difficulties in describing the characteristics of protist plankton, and will be of great help to modelers who strive to understand the nuanced ecology of these organisms, including their complex predator-prey relationships and allometric interactions. The MDB's findings point to knowledge deficiencies regarding the sources of nutrients (involving nitrate use, prey characteristics, and nutritional condition) for diverse mixoplankton functional groups, and the determination of crucial vital rates (like growth, reproduction, and survival rates). Growth, photosynthesis, and ingestion are linked biological functions, with factors influencing phototrophy and phagocytosis playing crucial roles in shaping their dynamics. Protistan phytoplankton and zooplankton within existing plankton databases can now be revisited and reclassified, illuminating their contributions to marine ecosystem dynamics.
Polymicrobial biofilms, frequently causing chronic infections, often prove resistant to effective treatment, largely due to their enhanced tolerance to antimicrobial agents. Interspecific interactions are recognized as factors affecting the development of polymicrobial biofilms. learn more However, the underlying contribution of diverse bacterial species cohabiting within polymicrobial biofilms is not yet fully elucidated. The presence of Enterococcus faecalis, Escherichia coli O157H7, and Salmonella enteritidis was examined in terms of its effect on establishing a collaborative triple-species biofilm. The coexistence of these three species, according to our findings, contributed to an increase in biofilm bulk and instigated a rearrangement of the biofilm, assuming a tower-like morphology. Compared to the E. faecalis mono-species biofilm, the triple-species biofilm's extracellular matrix (ECM) showed considerable variations in the proportion of polysaccharides, proteins, and eDNAs. Finally, we investigated the transcriptomic expression of *E. faecalis* during its coexistence with *E. coli* and *S. enteritidis* in a triple-species biofilm. The results highlight *E. faecalis*'s ability to dominate and reconfigure the triple-species biofilm. This was accomplished by improving nutrient flow, boosting amino acid production, increasing central carbon metabolism, influencing the microenvironment with biological strategies, and activating flexible stress response systems. Through a static biofilm model, the results of this pilot study expose the characteristics of E. faecalis-harboring triple-species biofilms, leading to novel insights into interspecies interactions and providing a foundation for clinical strategies to combat polymicrobial biofilms. The unique attributes of bacterial biofilm communities profoundly impact various elements of our everyday lives. Biofilms are remarkably tolerant to chemical disinfectants, antimicrobial agents, and the host's immune defenses. Multispecies biofilms, in the natural order, are the most prominent and widespread biofilm type. In this regard, a substantial requirement exists for further research designed to pinpoint the nature of multispecies biofilms and the influence of their properties on the growth and survival rates of the biofilm community. The influence of the coexistence of Enterococcus faecalis, Escherichia coli, and Salmonella enteritidis on triple-species biofilm formation is examined using a static model. Through transcriptomic analyses, this pilot study aims to uncover the potential underlying mechanisms behind the dominance of E. faecalis in triple-species biofilms. Our research provides fresh perspectives on triple-species biofilms, emphasizing that the composition of multispecies biofilms should be a primary factor when selecting antimicrobial treatments.
Public health is significantly concerned by the emergence of carbapenem resistance. The frequency of infections linked to carbapenemase-producing Citrobacter spp., and notably C. freundii, is demonstrating an upward trend. In tandem, a comprehensive global genomic dataset on carbapenemase-producing Citrobacter species is presently available. They are not readily found. To characterize the molecular epidemiology and international dissemination of 86 carbapenemase-producing Citrobacter species, short read whole-genome sequencing was utilized. Information gathered from two distinct surveillance programs active between 2015 and 2017. The common carbapenemases included KPC-2 (26%), VIM-1 (17%), IMP-4 (14%), and NDM-1 (10%), respectively. Of the observed species, C. freundii and C. portucalensis were the most significant. A variety of C. freundii clones were discovered, with the majority originating from Colombia (featuring KPC-2), the United States (featuring KPC-2 and KPC-3), and Italy (carrying VIM-1). Among the prevalent *C. freundii* clones, ST98 exhibited blaIMP-8 from Taiwan alongside blaKPC-2 from the United States. In contrast, ST22 exhibited blaKPC-2 from Colombia and blaVIM-1 from Italy. Two clones, ST493 (with blaIMP-4, restricted to Australia) and ST545 (with blaVIM-31, restricted to Turkey), accounted for the majority of C. portucalensis. The circulation of the Class I integron (In916) with blaVIM-1 was observed across numerous sequence types (STs) in Italy, Poland, and Portugal. Amongst various STs in Taiwan, the In73 strain, which carried the blaIMP-8 gene, was circulating, in contrast to the In809 strain, containing the blaIMP-4 gene, circulating between disparate STs in Australia. Carbapenemase-producing Citrobacter spp. pose a significant global challenge. The presence of STs, various in characteristics and spread throughout varied geographical areas, necessitates consistent monitoring of the population. Methods for genomic surveillance of Clostridium species should effectively discriminate between Clostridium freundii and Clostridium portucalensis. learn more Citrobacter species play a crucial role, the importance of which is undeniable. These issues are gaining recognition as substantial factors in hospital-acquired infections among humans. The carbapenemase-producing strains among Citrobacter species are a source of significant global health concern because they evade treatment with essentially every beta-lactam antibiotic. This document explicates the molecular makeup of a global collection of Citrobacter species, which demonstrate carbapenemase production. The carbapenemase-producing Citrobacter species most frequently observed in this survey were Citrobacter freundii and Citrobacter portucalensis. The erroneous identification of C. portucalensis as C. freundii through the use of Vitek 20/MALDI-TOF MS (matrix-assisted laser desorption/ionization-time of flight mass spectrometry) procedures necessitates a careful re-evaluation of future survey strategies. Among *C. freundii*, two prominent clones emerged: ST98, distinguished by blaIMP-8 from Taiwan and blaKPC-2 from the United States; and ST22, distinguished by blaKPC-2 from Colombia and blaVIM-1 from Italy. In the C. portucalensis species, ST493, characterized by blaIMP-4, was predominantly found in Australia, and ST545, characterized by blaVIM-31, was predominantly found in Turkey.
Cytochrome P450 enzymes demonstrate considerable promise as industrial biocatalysts, distinguished by their ability to catalyze site-selective C-H oxidation, coupled with a spectrum of catalytic reactions and a large substrate scope. An in vitro assay of conversion demonstrated the 2-hydroxylation capacity of CYP154C2, sourced from Streptomyces avermitilis MA-4680T, for androstenedione (ASD). The crystal structure of CYP154C2, complexed with testosterone (TES), was solved at 1.42 Å resolution, and this structure was leveraged to engineer eight mutants, including single, double, and triple mutants, with the intent of optimizing conversion efficiency. learn more In comparison to the wild-type (WT) enzyme, mutants L88F/M191F and M191F/V285L achieved markedly higher conversion rates, demonstrating 89-fold and 74-fold enhancements for TES, and 465-fold and 195-fold increases for ASD, respectively, while retaining high 2-position selectivity. Compared to the wild-type CYP154C2 enzyme, the L88F/M191F mutant exhibited a heightened substrate binding affinity for TES and ASD, consistent with the elevated conversion rates. Moreover, the L88F/M191F and M191F/V285L mutants experienced a significant augmentation in both the total turnover rate and kcat/Km. Surprisingly, the presence of L88F in all mutants led to the formation of 16-hydroxylation products, suggesting a pivotal role of L88 in CYP154C2's substrate selectivity and indicating that the corresponding amino acid to L88 within the 154C subfamily influences the binding orientation of steroids and substrate preference. The medicinal efficacy of hydroxylated steroid derivatives is profoundly impactful. The selective hydroxylation of methyne groups on steroid structures by cytochrome P450 enzymes can dramatically impact their polarity, biological efficacy, and toxicity. Steroid 2-hydroxylation is poorly represented in the literature; documented 2-hydroxylase P450 enzymes exhibit exceptionally low conversion efficiency and/or low selectivity in regio- and stereochemical aspects. This study's investigation into CYP154C2's crystal structure, combined with structure-guided rational engineering, effectively boosted the conversion efficiency of both TES and ASD, with noteworthy regio- and stereoselectivity.