Publications

4513

Abstract Vitamin B1 is a universally required coenzyme in carbon metabolism. However, most marine microorganisms lack the complete biosynthetic pathway for this compound and must acquire thiamin, or precursor molecules, from the dissolved pool. The most common version of Vitamin B1 auxotrophy is for thiamin's pyrimidine precursor moiety, 4‐amino‐5‐hydroxymethyl‐2‐methylpyrimidine (HMP). Frequent HMP auxotrophy in plankton and vanishingly low dissolved concentrations (approximately 0.1–50 pM) suggest that high‐affinity HMP uptake systems are responsible for maintaining low ambient HMP concentrations. We used tritium‐labelled HMP to investigate HMP uptake mechanisms and kinetics in cell cultures of Candidatus Pelagibacter st. HTCC7211, a representative of the globally distributed and highly abundant SAR11 clade. A single protein, the sodium solute symporter ThiV, which is conserved across SAR11 genomes, is the likely candidate for HMP transport. Experimental evidence indicated transport specificity for HMP and mechanistically complex, high‐affinity HMP uptake kinetics. Km values ranged from 9.5 pM to 1.2 nM and were dramatically lower when cells were supplied with a carbon source. These results suggest that HMP uptake in HTCC7211 is subject to complex regulation and point to a strategy for high‐affinity uptake of this essential growth factor that can explain natural HMP levels in seawater.

AbstractMetagenomic analysis was conducted to assess the microbial community in the high‐altitude Tamdykul geothermal spring in Tajikistan. This analysis yielded six high‐quality bins from the members of Thermaceae, Aquificaceae, and Halothiobacillaceae, with a 41.2%, 19.7%, and 18.1% share in the total metagenome, respectively. Minor components included Schleiferia thermophila (1.6%) and members of the archaeal taxa Pyrobaculum (1.2%) and Desulfurococcaceae (0.7%). Further analysis of the metagenome‐assembled genome (MAG) from the Desulfurococcaceae family (MAG002) revealed novel taxonomy with only 80.95% closest placement average nucleotide identity value to its most closely related member of the Desulfurococcaceae family, which is part of the Thermoproteota phylum comprising hyperthermophilic members widespread in geothermal environments. MAG002 consisted of 1.3 Mbp, distributed into 48 contigs with 1504 predicted coding sequences, had an average GC content of 41.3%, a completeness and contamination rate of 98.7% and 2.6%, respectively, and branched phylogenetically between the Ignisphaera and Zestosphaera lineages. Digital DNA‐DNA hybridization values compared with Ignisphaera aggregans and Zestosphaera tikiterensis were 33.7% and 19.4%, respectively, suggesting that this MAG represented a novel species and genus. Its 16S rRNA gene contained a large 421 bp intron. It encodes a complete gluconeogenesis pathway involving a bifunctional fructose‐1,6‐bisphosphate phosphatase/aldolase; however, the glycolysis pathway is incomplete. The ribulose monophosphate pathway enzymes could be used for pentose synthesis. MAG002 encodes several hydrogen‐evolving hydrogenases, with possible roles as hydrogen sinks during fermentation. We propose the name Zestomicrobium tamdykulense gen. nov. sp. nov. for this organism; it is the first thermophilic genome reported from Tajikistan.

AbstractCulture collections such as the Blue Biotechnology and Ecotoxicology Culture Collection (LEGE‐CC) hold approximately 1200 cyanobacterial strains and are critical community resources. However, many isolates in this and other collections have not been described with a polyphasic approach, and this limits further study. Here, we employed a polyphasic methodology that integrates 16S rRNA gene phylogenetic analyses, similarity (p‐distance), 16S‐23S ITS rRNA region secondary structures, morphological analyses, and habitat assessments to describe four novel cyanobacterial genera from the LEGE‐CC, Portugal. Pseudolimnococcus planktonicus gen. et sp. nov. (Chroococcales) is phylogenetically and morphologically related to Limnococcus. The 16S rRNA gene similarity between the types of both genera is only 93.1%. Morphologically, Pseudolimnococcus cells do not reach the original spherical shape before the next division or have aerotopes and firm mucilage, while Limnococcus cells reach the original shape, lack aerotopes, and have diffluent mucilage. Eucapsopsis lusitanus gen. et sp. nov. (Chroococcales) is morphologically similar to Eucapsis but differs from it by having aerotopes and diffluent envelope. Eucapsis lacks aerotopes and has firm mucilaginous envelopes, rarely diffluent. Both genera are phylogenetically very distant from each other and have only 90.68% 16S rRNA gene similarity. Pseudoacaryochloris arrabidensis gen. et sp. nov. (Acaryochloridales) differs from Acaryochloris by the lack of mucilaginous envelope, which is present in Acaryochloris. Both genera are phylogenetically distant and have only 94.1% 16S rRNA gene similarity. Moreover, Acaryochloris is marine (sponge symbiont), while Pseudoacaryochloris is from freshwater. Vasconcelosia minhoensis gen. et sp. nov. (Nodosilineales) is phylogenetically related to Cymatolege but has only 94.3% similarity with this genus. Morphologically both genera are distinct. Vasconcelosia has a Romeria‐like structure, while Cymatolege has a Phormidium‐like structure. In all cases the 16S‐23S ITS rRNA region secondary structures are in agreement with the other analyses. These novel genera expand the diversity of cyanobacteria in culture collections.

‘Candidatus Phytoplasma brasiliense’ (CPB) is a phytoplasma originally discovered in South America and is known to infect a wide variety of economically important crops. It is most prevalent in Hibiscus spp., where it causes witches broom symptoms, and papaya, where it causes bunchy top. Recently, CPB was documented for the first time in North America in a new host, globe sedge. In this study, two quantitative PCR assays are developed: one using high-resolution melt curve analysis (HRMA) based on the secA gene and the other a TaqMan assay based on the dnaK gene. The secA/HRMA and dnaK/TaqMan assay successfully amplified two of the three isolates of CPB. Both assays were screened against available isolates of 16SrI, 16SrII, and 16SrIV phytoplasmas. The secA/HRMA assay failed to amplify 16SrI and 16SrIV phytoplasmas but successfully amplified 16SrII phytoplasmas. The resulting melting point (Tm) products of CPB and 16SrII phytoplasmas displayed a difference of 0.5°C, easily distinguishing them by melt curves. The dnaK/TaqMan assay failed to amplify all non-CPB phytoplasma isolates in the study. The development of these assays provides a valuable tool that will significantly improve monitoring programs in Florida and will aid in developing a better fundamental understanding of the epidemiology of this phytoplasma.

AbstractGut microbiota dysbiosis has been implicated in rheumatoid arthritis (RA) and influences disease progression. Although molecular and culture‐independent studies revealed RA patients harbored a core microbiome and had characteristic bacterial species, the lack of cultured bacterial strains had limited investigations on their functions. This study aimed to establish an RA‐originated gut microbial biobank (RAGMB) that covers and further to correlates and validates core microbial species on clinically used and diagnostic inflammation and immune indices. We obtained 3200 bacterial isolates from fecal samples of 20 RA patients with seven improved and 11 traditional bacterial cultivation methods. These isolates were phylogenetically identified and selected for RAGMB. The RAGMB harbored 601 bacterial strains that represented 280 species (including 43 novel species) of seven bacterial phyla. The RAGMB covered 93.2% at species level of medium‐ and high‐abundant (relative abundances ≥0.2%) RA gut microbes, and included four rare species of the phylum Synergistota. The RA core gut microbiome was defined and composed of 20 bacterial species. Among these, Mediterraneibacter tenuis and Eubacterium rectale were two species that statistically and significantly correlated with clinically used diagnostic indices such as erythrocyte sedimentation rate (ESR) and IL‐10. Thus, M. tenuis and E. rectale were selected for experimental validation using DSS‐treated and not DSS‐treated mice model. Results demonstrated both M. tenuis and E. rectale exacerbated host inflammatory responses, including shortened colon length and increased spleen weight, decreased IL‐10 and increased IL‐17A levels in plasma. Overall, we established the RAGMB, defined the RA core microbiome, correlated and demonstrated core microbial species effected on host inflammatory and immune responses. This work provides diverse gut microbial resources for future studies on RA etiology and potential new targets for new biomedical practices.