Publications

4532

Summary The KTK 4A‐related Thermoplasmata thrives in the sediment of saline lakes; however, systematic research on its taxonomy, environmental adaptation and metabolism is lacking. Here, we detected this abundant lineage in the sediment of five artificially separated ponds (salinity 7.0%–33.0%) within a Chinese soda‐saline lake using culture‐independent metagenomics and archaeal 16S rRNA gene amplicons. The phylogenies based on the 16S rRNA gene, and 122 archaeal ubiquitous single‐copy proteins and genome‐level identity analyses among the metagenome‐assembled genomes demonstrate this lineage forming a novel order, Candidatus Haloplasmatales, comprising four genera affiliated with the identical family. Isoelectric point profiles of predicted proteomes suggest that most members adopt the energetically favourable ‘salt‐in’ strategy. Functional prediction indicates the lithoheterotrophic nature with the versatile metabolic potentials for carbohydrate and organic acids as well as carbon monoxide and hydrogen utilization. Additionally, hydrogenase genes hdrABC ‐ mvhADG are linked with incomplete reductive citrate cycle genes in the genomes, suggesting their functional connection. Comparison with the coupling of HdrABC‐MvhADG and methanogenesis pathway provides new insights into the compatibility of laterally acquired methanogenesis with energy metabolism in the related order Methanomassiliicoccales . Globally, our research sheds light on the taxonomy, environmental adaptative mechanisms, metabolic potentials and evolutional significance of Ca . Haloplasmatales.

Abstract “ Candidatus Liberibacter solanacearum” (Lso), transmitted by the potato psyllid ( Bactericera cockerelli ), is the causal agent of potato zebra chip, but can also infect other solanaceous plants, including peppers. Studies were conducted to investigate whether Lso could be transmitted to the next generation of plants through seeds from infected pepper plants. In 2014, jalapeno pepper plants were infested with psyllids carrying a mixture of Lso A and B (AB) at the AgriLife Research Station at Bushland. The study was again conducted in 2019 and pepper plants were infested with psyllids carrying Lso B or Lso AB. In each of the studies, noninfested plants served as controls. At harvest, fruits were collected and tested for the presence of Lso using quantitative PCR. Seeds from infected fruits were then tested for Lso. Overall, the percentage of seeds that tested positive for Lso ranged from 33% to 70%. However, Lso detection in embryos ranged only from 0% to 8%. Seed samples from Lso‐positive fruits were planted in the greenhouse to determine the impact of Lso on emergence and the incidence of Lso in emerged plants. Although plant emergence differed between some of the seeds obtained from Lso‐positive and ‐negative fruits, the overall impact of Lso on plant emergence was not consistent. However, of the 182 plants that emerged from seeds collected from infected fruits, none was positive for Lso, suggesting that seeds are unlikely to serve as sources for new Lso infections and their impact on disease epidemiology is negligible.