General Medicine

El Huanglongbing (HLB) es una enfermedad considerada como la más destructiva para los cítricos en el mundo, es causada por Candidatus Liberibacter asiaticus (CLas) y diseminada por el vector Diaphorina citri. El HLB ha generado cuantiosas pérdidas económicas en la citricultura mundial. Todas las variedades comerciales de cítricos son susceptibles a esta enfermedad. La naturaleza de CLas como parásito intra celular estricto limitado al floema dificulta el estudio fitopatológico de la enfermedad. Las herramientas “ómicas”, que permiten aplicar análisis comparativos con enfoque masivos, han resultado útiles para describir la interacción entre el agente patogénico y diferentes especies de cítricos, generando conocimiento sobre las bases moleculares de la patogenicidad de CLas y de las respuestas de los hospederos ante la infección. Sin embargo, muchos procesos inmersos en la compleja interacción CLas-cítricos aún no son del todo comprendidos. En la presente revisión se resumen algunos de los principales hallazgos en la última década relacionados con los posibles mecanismos de patogenicidad de CLas a nivel molecular, así como de las respuestas transcripcionales y metabólicas inducidas en cítricos tolerantes o susceptibles, ante la infección. Este conocimiento es necesario para el diseño e implementación de nuevas estrategias para el manejo sustentable de la enfermedad.

Candidatus Liberibacter asiaticus (CLas) se ha dispersado rápidamente a las regiones productoras de cítricos en México, ocasionando impactos económicos y sociales diferenciados. En México, los principales avances en investigación se han centrado en el manejo del vector, Diaphorina citri y en estudios de la interacción de CLas con limón mexicano. Sin embargo, la variabilidad genética de la bacteria en regiones productoras de México se ha estudiado poco. Por lo que, en el presente estudio se analizó la variación de la población mexicana de CLas con procedimientos basados en PCR, secuenciación y electroforesis capilar a través de la detección del número de repeticiones en tándem (TRN) con dos marcadores STR, AGACACA y TACAGAA, el primero localizado en locus genómicos CLIBASIA_01645 y adenosina deaminasas. La distribución de los TRNs en la población mexicana de CLas en ambos loci mostraron variaciones con las poblaciones previamente reportadas en Florida, China y Brasil. Además, en la población mexicana se encontraron tres haplotipos, HA, HB y HC, siendo el primer reporte del haplotipo HC en las regiones citrícolas en México. Interesantemente, las subpoblaciones de CLas del Occidente y Noroeste son diferentes a la del Sureste.

Huanglongbing (HLB), caused by the Candidatus Liberibacter spp., is the most devastating disease in the citrus industry. HLB significantly affects and alters the microbial community structure or potential function of the microbial community of leaves and roots. However, it is unknown how the microbial community structure of the pericarp with different pigments is affected by Candidatus Liberibacter asiaticus (CLas). This study identified the enriched taxa of the microbial community in the citrus pericarp with normal or abnormal pigment and determine the effects of HLB on the pericarp microbial community using 16S rRNA-seq. The alpha and beta diversity and composition of microbial communities were significantly different between normal and abnormal pigment pericarp tissues of ripe fruits infected by CLas. Firmicutes, Actinobacteriota, Bacteroidota, Acidobacteriota, and Desulfobacterota dominated the pericarp microbiota composition in WDYFs (whole dark yellow fruits) samples. The relative abundance of most genera in WDYFs was higher than 1%, such as Burkholderia, and Pelomonas. However, with the exception of the HLB pathogen, the relative abundance of most genera in the abnormal-colored pericarp samples was less than 1%. CLas decreased the relative abundance of pericarp taxonomic. The predicted function of microbial was more plentiful and functional properties in the WDYF sample, such as translation, ribosomal structure and biogenesis, amino acid transport and metabolism, energy production and conversion, and some other clusters of orthologous groups (COG) except for cell motility. The results of this study offer novel insights into understanding the composition of microbial communities of the CLas-affected citrus pericarps and contribute to the development of biological control strategies for citrus against Huanglongbing.

AbstractMarine sediments comprise one of the largest environments on the planet, and their microbial inhabitants are significant players in global carbon and nutrient cycles. Recent studies using metagenomic techniques have shown the complexity of these communities and identified novel microorganisms from the ocean floor. Here, we obtained 77 metagenome-assembled genomes (MAGs) from the bacterial phylum Armatimonadota in the Guaymas Basin, Gulf of California, and the Bohai Sea, China. These MAGs comprise two previously undescribed classes within Armatimonadota, which we propose naming Hebobacteria and Zipacnadia. They are globally distributed in hypoxic and anoxic environments and are dominant members of deep-sea sediments (up to 1.95% of metagenomic raw reads). The classes described here also have unique metabolic capabilities, possessing pathways to reduce carbon dioxide to acetate via the Wood-Ljungdahl pathway (WLP) and generating energy through the oxidative branch of glycolysis using carbon dioxide as an electron sink, maintaining the redox balance using the WLP. Hebobacteria may also be autotrophic, not previously identified in Armatimonadota. Furthermore, these Armatimonadota may play a role in sulfur and nitrogen cycling, using the intermediate compounds hydroxylamine and sulfite. Description of these MAGs enhances our understanding of diversity and metabolic potential within anoxic habitats worldwide.

Abstract CVPD disease (Huanglongbing) is the most severe citrus disease caused by the bacterium Cand. Liberibacter asiaticus. This pathogen lives in the phloem tissue of citrus plants and is transmitted through the vector Diaphorina citri and by grafting. The study aimed to know the presence of CVPD disease in Orange cv Selayar nurseries and mother tree gardens in the Selayar Islands Regency. The PCR test was carried out in the research using the Laboratory of Agricultural Biotechnology, Hasanuddin University. The DNA of the citrus leaves was extracted using the Genomic DNA Kit method and the DNA CLas was amplified using the polymerase chain reaction (PCR) with the primer pairs OI1-O12c. The results showed that the percentage of mother plants of orange cv. Selayar infected with CVPD-like symptoms were 10-21 %. The percentage of citrus seedlings with CVPD-like symptoms in 2 nurseries were 0.27% and 0.09%. The symptoms of CVPD disease have been confirmed using a PCR technique, which was successful in amplifying the DNA fragment of CLa measuring 1160 bp, although not all symptoms suspected of CVPD are confirmed positive.

AbstractCandidatus Branchiomonas cysticola is recognized as the most prevalent bacterial agent causing epitheliocystis in Atlantic salmon (Salmo salar). Based on its partial 16S rRNA sequence, the bacterium has previously been found to be a member of Burkholderiales in the class Betaproteobacteria. Multilocus Sequence Analysis (MLSA) of the bacterium and 60 type strains of Betaproteobacteria using newly identified housekeeping genes (dnaK, rpoC, and fusA) and ribosomal subunit sequences (16S and 23S), instead supported the bacterium’s affiliation to Nitrosomodales. Taxonomic rank normalization by Relative Evolutionary Divergence (RED) showed the phylogenetic distinction between Cand. B. cysticola and its closest related type strain to be at the family level. A novel bacterial family named Branchiomonaceae has thus been proposed to include a monophyletic clade of Betaproteobacteria exclusively associated with epitheliocystis in fish.

An updated real-time multiplex quantitative polymerase chain reaction (qPCR) assay was designed and validated for the simultaneous detection of three ‘ Candidatus Liberibacter species’ (CLsp), ‘ Ca. Liberibacter asiaticus’ (CLas), ‘africanus’ (CLaf), and ‘americanus’ (CLam), associated with the huanglongbing disease of citrus. The multiplex assay was designed based on the qPCR assay published in 2006 by Li et al., considering all available CLsp 16S rRNA gene sequences in GenBank and the MIQE guidelines and workflow for qPCR optimization, which became available after 2006. When using the updated multiplex CLsp qPCR assay compared with singleplex qPCR, no significant increase in quantitative cycle (Cq) values was detected. The specificity and sensitivity of the updated qPCR assay was optimal, and measuring the intra- and interassay variations confirmed the reproducibility and repeatability of the assay. The assay was also successfully used with a large number of diverse samples at independent laboratories in four countries, thus demonstrating its transferability, applicability, practicability, and robustness as different qPCR reaction conditions or instruments had a minor effect on Cq values. This updated multiplex CLsp qPCR assay can be used in a variety of citrus surveys, germplasm, or nursery stock programs that require different pathogen detection tools for their successful operation. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Huanglongbing, a globally devastating citrus disease, is associated with Candidatus Liberibacter asiaticus (CLas) and is mainly transmitted by Diaphorina citri. Verification of the distribution and dynamics of CLas in D. citri is critical to understanding CLas transmitted by vectors in nature. Here, the distribution and titers of CLas in different sexes and tissues of D. citri adults were investigated by fluorescence in-situ hybridization (FISH) and quantitative real-time PCR (qRT-PCR). Results showed that CLas had widespread distribution in the brain, salivary glands, digestive system, and reproductive system of both females and males, indicating a systemic infection of CLas in D. citri. Moreover, CLas fluorescence intensity and titers were significantly increased in both the digestive system and the female reproductive system with development and there was a marked decreased in both the salivary glands and the male brain, but there was no significant change in the female brain or the male reproductive system. Furthermore, the distribution and dynamics of CLas in embryos and nymphs were investigated. CLas was observed in all laid eggs and subsequent first–second-instar nymphs, indicating that a high percentage of embryos and nymphs resulting from infected D. citri mothers were infected with CLas.