Publications

4364

Candidatus Accumulibacter belongs to phosphate-accumulating organisms (PAO) which exhibit cyclic metabolism and are capable of intracellular polyphosphate accumulation and their hydrolysis under feast-famine anaerobic-aerobic cycling. In consortia of activated sludge microorganisms, these bacteria are responsible for enhanced biological phosphorus removal (EBPR). The spectrum of the substrates used by Ca. Accumulibacter remains insufficiently studied. It was investigated by measuring the oxygen uptake rates (OUR) of Ca. Accumulibacter-enriched culture supplemented with 17 different organic substrates. The highest oxygen uptake rates values were observed in the presence of tryptone, volatile fatty acids (acetate, propionate, and butyrate), succinate, pyruvate, and amino acids (aspartate and glutamate). Phosphate dynamics in the medium under shifts from anaerobic to aerobic cultivation in batch experiments was studied for these compounds (except for tryptone). All tested substrates were shown to cause phosphate cycling (release in the anaerobic phase and uptake in the aerobic one), with OURs for the substrates correlating with the amount of phosphates consumed during the aerobic phase. It was concluded that OUR may be used as an indicator of the monosubstrates used by Ca. Accumulibacter in the anaerobic/aerobic cycle. The possible pathways for substrate transport and metabolism by Ca. Accumulibacter are discussed using the stoichiometric data and the results of metagenomic analysis.

Abstract Background Candidatus Ornithobacterium hominis (O. hominis), which was found in Egyptian nasopharyngeal swabs but remains unidentified, has been associated with respiratory disorders in humans. Herein, we presented two draft genome assemblies of O. hominis that were extracted from metagenomic data using the Illumina sequencing method. The primary goal of this study was to present the first O. hominis genome sequence from Egyptian populations. Results The genome size was estimated to be 1,931,660 base pairs (bp), with 1,837 predicted coding regions and a G + C content of 35.62%. The toxA gene, 20 antibiotic resistance genes, and gliding motility genes were found in the genome assembly. Gliding motility lipoproteins (GldD, GldJ, GldN, and GldH) and the gliding motility-associated ABC transporter substrate-binding protein, which acts as a crucial virulence mechanism in Flavobacterium species, were identified. The genome contained unique proteins, such as the ParE1 toxin, that exhibit a defense mechanism against quinolone and other antibiotic actions. The cobalt-zinc-cadmium resistance protein CzcB, which is necessary for metal resistance, urease regulation, and colonization, was also detected. Several multidrug resistance proteins were identified, such as MexB, mdtK, yheI, and VanC. Conclusion Numerous virulence factors such as toxA and gliding motility genes, were present in the core O. hominis genome. Additionally, the draft genome contains several antibiotic-resistance genes. These findings may contribute to a better understanding of the genomic landscape of O. hominis and the identification of genes involved in virulence and antibiotic resistance.

Early detection and prompt response are key factors in the eradication of ‘huanglongbing’ (HLB) in California. Currently, qPCR testing of leaf tissue guides the removal of infected trees. However, because of the uneven distribution of ‘Candidatus Liberibacter asiaticus’ (CLas) in an infected tree and asymptomatic infection, selecting the best leaves to sample, from a mature tree with more than 200,000 estimated leaves, is a major hurdle for timely detection. The goal of this study was to address this issue by testing alternative tissues that might improve the CLas detection rate. Using two years of field data, old and young leaves, peduncle bark of fruit, and feeder roots were evaluated for the presence of CLas. Quadrant-peduncle (Q-P) tissue sampling consistently resulted in better CLas detection than any other tissue type. Q-P samples had a 30% higher qPCR positivity rate than quadrant-leaf (Q-L) samples. No significant seasonal patterns were observed. Roots and single peduncles had similar detection rates; both were higher than single leaves or Q-L samples. If symptoms were used to guide sampling, 30% of infected trees would have been missed. Taken together, these results suggest that Q-P tissue sampling is the optimal choice for improved CLas detection under California growing conditions.

Members of the archaeal order Caldarchaeales (previously the phylum Aigarchaeota) are poorly sampled and are represented in public databases by relatively few genomes. Additional representative genomes will help resolve their placement among all known members of Archaea and provide insights into their roles in the environment. In this study, we analyzed 16S rRNA gene amplicons belonging to the Caldarchaeales that are available in public databases, which demonstrated that archaea of the order Caldarchaeales are diverse, widespread, and most abundant in geothermal habitats. We also constructed five metagenome-assembled genomes (MAGs) of Caldarchaeales from two geothermal features to investigate their metabolic potential and phylogenomic position in the domain Archaea. Two of the MAGs were assembled from microbial community DNA extracted from fumarolic lava rocks from Mauna Ulu, Hawai‘i, and three were assembled from DNA obtained from hot spring sinters from the El Tatio geothermal field in Chile. MAGs from Hawai‘i are high quality bins with completeness >95% and contamination <1%, and one likely belongs to a novel species in a new genus recently discovered at a submarine volcano off New Zealand. MAGs from Chile have lower completeness levels ranging from 27 to 70%. Gene content of the MAGs revealed that these members of Caldarchaeales are likely metabolically versatile and exhibit the potential for both chemoorganotrophic and chemolithotrophic lifestyles. The wide array of metabolic capabilities exhibited by these members of Caldarchaeales might help them thrive under diverse harsh environmental conditions. All the MAGs except one from Chile harbor putative prophage regions encoding several auxiliary metabolic genes (AMGs) that may confer a fitness advantage on their Caldarchaeales hosts by increasing their metabolic potential and make them better adapted to new environmental conditions. Phylogenomic analysis of the five MAGs and over 3,000 representative archaeal genomes showed the order Caldarchaeales forms a monophyletic group that is sister to the clade comprising the orders Geothermarchaeales (previously Candidatus Geothermarchaeota), Conexivisphaerales and Nitrososphaerales (formerly known as Thaumarchaeota), supporting the status of Caldarchaeales members as a clade distinct from the Thaumarchaeota.

AbstractTaurine-respiring gut bacteria produce H2S with ambivalent impact on host health. We report the isolation and ecophysiological characterization of a taurine-respiring mouse gut bacterium. Taurinivorans muris strain LT0009 represents a new widespread species that differs from the human gut sulfidogen Bilophila wadsworthia in its sulfur metabolism pathways and host distribution. T. muris specializes in taurine respiration in vivo, seemingly unaffected by mouse diet and genotype, but is dependent on other bacteria for release of taurine from bile acids. Colonization of T. muris in gnotobiotic mice increased deconjugation of taurine-conjugated bile acids and transcriptional activity of a sulfur metabolism gene-encoding prophage in other commensals, and slightly decreased the abundance of Salmonella enterica, which showed reduced expression of galactonate catabolism genes. Re-analysis of metagenome data from a previous study further suggested that T. muris can contribute to protection against pathogens by the commensal mouse gut microbiota. Together, we show the realized physiological niche of a key murine gut sulfidogen and its interactions with selected gut microbiota members.

Two metagenome-assembled genomes (MAGs), GKL-01 and GKL-02, related to the family Thiotrichaceae have been assembled from the metagenome of bacterial mat obtained from a sulfide-rich thermal spring in the North Caucasus. Based on average amino acid identity (AAI) values and genome-based phylogeny, MAG GKL-01 represented a new genus within the Thiotrichaceae family. The GC content of the GKL-01 DNA (44%) differed significantly from that of other known members of the genus Thiothrix (50.1–55.6%). We proposed to assign GKL-01 to a new species and genus ‘Candidatus Thiocaldithrix dubininis’ gen. nov., sp. nov. GKL-01. The phylogenetic analysis and estimated distances between MAG GKL-02 and the genomes of the previously described species of the genus Thiothrix allowed assigning GKL-02 to a new species with the proposed name ‘Candidatus Thiothrix putei’ sp. nov. GKL-02 within the genus Thiothrix. Genome data first revealed the presence of both Na+-ATPases and H+-ATPases in several Thiothrix species. According to genomic analysis, bacteria GKL-01 and GKL-02 are metabolically versatile facultative aerobes capable of growing either chemolithoautotrophically or chemolithoheterotrophically in the presence of hydrogen sulfide and/or thiosulfate or chemoorganoheterotrophically.

AbstractCoral microhabitats are colonized by a myriad of microorganisms, including diverse bacteria which are essential for host functioning and survival. However, the location, transmission, and functions of individual bacterial species living inside the coral tissues remain poorly studied. Here, we show that a previously undescribed bacterial symbiont of the coralPocillopora acutaforms cell-associated microbial aggregates (CAMAs) within the mesenterial filaments. CAMAs were found in both adults and larval offspring, providing evidence of vertical transmission.In situlaser capture microdissection of CAMAs followed by 16S rRNA gene metabarcoding and shotgun metagenomics produced a near complete metagenome-assembled genome. We subsequently cultured the CAMA bacteria fromP. acutacolonies, and sequenced and assembled their genomes. Phylogenetic analyses showed that the CAMA bacteria belong to an undescribed Endozoicomonadaceae genus and species, which we propose to nameSororendozoicomonas aggregatagen. nov sp. nov. Metabolic pathway reconstruction from its genome sequence suggests this species can synthesize most amino acids, several B vitamins, and antioxidants, which may be beneficial to its coral hosts. This study provides detailed insights into a new member of the widespread Endozoicomonadaceae family, thereby improving our understanding of coral holobiont functioning. Vertically transmitted, tissue-associated bacteria, such asS. aggregatamay be key candidates for the development of microbiome manipulation approaches with long-term positive effects on the coral host.