Publications

4367

AbstractBACKGROUNDAlthough it is known that Candidatus Liberibacter asiaticus (CLas), the agent of citrus Huanglongbing, circulates and multiplies within the insect vector Diaphorina citri, the specific factors enabling CLas transmission remain unclear. Previous studies have shown that ATPSyn‐β facilitates phytoplasma movement in vector insects, and functions as a transport protein in D. citri. In this study, the role of ATPSyn‐β was expected to be unveiled in CLas transmission in D. citri.RESULTSThe interaction between ATPSyn‐β of D. citri and the outer membrane protein A (OmpA) of CLas was identified using glutathione S‐transferase pull‐down and yeast two‐hybrid assays. No interactions existed between OmpA and vitellogenin (Vg). Bioinformatics analysis revealed that ATPSyn‐β contained two conserved domains, ATP‐synt_ab_N and ATP‐synt_ab. Notably, ATP‐synt_ab_N interacted with both OmpA and Vg, indicating a competitive relationship between Vg and OmpA for binding to ATPSyn‐β. After silencing ATPSyn‐β expression using RNAi, the feeding behavior of D. citri decreased, resulting in a lower acquisition of CLas. Subsequently, this inhibited CLas movement within D. citri and reduced the inoculation of CLas to healthy citrus plants.CONCLUSIONATPSyn‐β was involved in the acquisition, movement in vivo, and inoculation of CLas by interacting with OmpA, thus offering a novel target to prevent the spread of citrus Huanglongbing. © 2025 Society of Chemical Industry.

AbstractPurple sulfur bacteria (PSB) of the family Chromatiaceae (Gammaproteobacteria) can perform chemo‐ and photo‐lithoautotrophy (through anoxygenic photosynthesis) in anoxic layers of freshwater stratified (including meromictic) lakes. This group has been extensively studied via physiological and ecological approaches, albeit their genomics has lagged behind. Here, we monitored a small, shallow, karstic lake, Lagunillo de Cardenillas, that developed a pink coloration throughout the whole water column and prevailed for ca. 2 years across seasons of the limnological cycle. Combining the study of physical/chemical parameters, amplicon sequencing, metagenomics, genomics, and microscopy, we observed this phenomenon was caused by blooms of a novel Thiocapsa species, which represented ca. 40% of the total microbial biomass of the lake's water column during the autumn/winter mixing period, and ca. 36% in the anoxic layers during spring/summer stratification. The dominance of this microbe was attributed to the high sulfur concentrations and biogeochemical features of the lake combined with various genomic footprints/abilities of this microbe to utilize different nutrient sources under anoxic and oxic/microaerophilic conditions. The latter included nitrogen (cyanate and ethanolamine hydrolysis, N fixation, dissimilatory nitrate reduction, ammonia assimilation, denitrification), carbon (anoxygenic photosynthesis and the presence of α‐carboxysomes and type IA RuBisCOs) and sulfur (dimethylsulfide [DMS] and thiosulfate oxidation, dimethylsulfoxide [DMSO] reduction). In addition, this novel species possessed genes for gas vesicle formation, anoxic/oxic respiration pathways, hydrogenases, oxic stress response, and a CRISPR‐Cas array. Thus, its extensive genomic repertoire helped explain its versatility and success in colonizing both the anoxic layers and the oxic/anoxic interphase in this lake.

Abstract Background Rare species, especially of the marine sedimentary biosphere, have long been overlooked owing to the complexity of sediment microbial communities, their sporadic temporal and patchy spatial abundance, and challenges in cultivating environmental microorganisms. In this study, we combined enrichments, targeted metagenomic sequencing, and extensive data mining to uncover uncultivated members of the archaeal rare biosphere in marine sediments. Results In protein-amended enrichments, we detected the ecologically and metabolically uncharacterized class Candidatus Penumbrarchaeia within the phylum Thermoplasmatota. By screening more than 8000 metagenomic runs and 11,479 published genome assemblies, we expanded the phylogeny of Ca. Penumbrarchaeia by 3 novel orders. All six identified families of this class show low abundance in environmental samples characteristic of rare biosphere members. Members of the class Ca. Penumbrarchaeia were predicted to be involved in organic matter degradation in anoxic, carbon-rich habitats. All Ca. Penumbrarchaeia families contain high numbers of taxon-specific orthologous genes, highlighting their environmental adaptations and habitat specificity. Besides, members of this group exhibit the highest proportion of unknown genes within the entire phylum Thermoplasmatota, suggesting a high degree of functional novelty in this class. Conclusions In this study, we emphasize the necessity of targeted, data-integrative approaches to deepen our understanding of the rare biosphere and uncover the functions and metabolic potential hidden within these understudied taxa.

Ticks spread pathogens that affect both human and animal health and often cause significant economic losses to the livestock industry. However, there is limited data on the distribution of ticks and tick-borne pathogens, particularly those affecting cattle in Cameroon. In this study, ticks were collected from cattle in Buea, the capital of the South West Region of Cameroon, to determine their diversity and identify tick-borne pathogens through PCR and sequencing. The tick samples were screened for pathogens using assays that target the rOmpA gene (ompA) of Rickettsia, the ssrRNA gene of Babesia and Theileria and the Ehrlichia genus 16SrRNA gene. A total of 458 ticks were collected with Rhipicephalus annulatus (65.6%) as the predominant species. From 68 tick pools screened, 26 (38.2%) were positive for pathogen/ symbiont DNA. The pathogen identified was Rickettsia africae (22.1%). This study reports the first molecular detection of the symbiont Candidatus Midichloria mitochondrii (22.1%) in the sampled tick species. It was observed that male ticks were significantly more likely to test positive for R. africae (OR = 208, 95% CI = 28.6 - 4553, p<0.001). Animal handlers may face the risk of these zoonotic infections and as such, there is a need to employ protective measures to prevent or reduce pathogen spread.

Despite their large environmental impact and multiple independent emergences, the processes leading to the evolution of anaerobic methanotrophic archaea (ANME) remain unclear. This work uses comparative metagenomics of a recently evolved but understudied ANME group, “ Candidatus Methanovorans” (ANME-3), to identify evolutionary processes and innovations at work in ANME, which may be obscured in earlier evolved lineages. We identified horizontal transfer of hdrA homologs and convergent evolution in carbon and energy metabolic genes as potential early steps in Methanovorans evolution. We also identified the erosion of genes required for methylotrophic methanogenesis along with horizontal acquisition of multiheme cytochromes and other loci uniquely associated with ANME. The assembly and comparative analysis of multiple Methanovorans genomes offers important functional context for understanding the niche-defining metabolic differences between methane-oxidizing ANME and their methanogen relatives. Furthermore, this work illustrates the multiple evolutionary modes at play in the transition to a globally important metabolic niche.

Abstract The CRISPR–Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated protein) systems are adaptive immune mechanisms that play critical roles in defending archaea and bacteria against invading entities. These systems can be divided into two classes, with class 2 comprising three types (II, V, and VI). Because of their ability to cleave double-stranded DNA, many class 2 CRISPR–Cas proteins have been harnessed as genome editing tools. Unlike the well-studied type II Cas9 proteins, the structural studies of the type V-B Cas12b proteins are limited, hindering their engineering and broader application. Here, we report four complex structures of ChCas12b, which reveal many unique structural features. The folding of the single guide RNA (sgRNA) of ChCas12b is distinct from that of AacCas12b and BthCas12b. Notably, many of these unique features are involved in ChCas12b–sgRNA interaction, suggesting that they are co-evolved. While ChCas12b shares a conserved two-cation-assisted catalytic mechanism with its homologs, it recognizes a longer guide:target heteroduplex, potentially offering higher fidelity in DNA editing. Altogether, our studies suggested that Cas12b family proteins exhibit significant diversity in their folding, sgRNA and target DNA binding. In the future, it is worth characterizing more representative proteins to identify CRISPR–Cas proteins with higher gene editing ability and fidelity.