Publications

4852

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.

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.