Publications

4994

Coconut lethal yellowing disease (CLYD) caused by phytoplasma is a destructive disease affecting coconut and other palm species. The disease has been reported in Mozambique, Tanzania, and some West African countries, where millions of coconut trees have been affected. Although the disease was first reported in 1999 in Northern Coast of Kenya, no further studies have been conducted, leaving the giant coconut industry at risk of destruction. It is for this reason that a surveillance was undertaken to study the extent of the disease spread and the specific Candidatus phytoplasma strain causing the disease. A total of 125 coconut tree samples were collected in Kwale, Kilifi, Lamu, and Tana River counties by drilling the tree trunks aseptically. DNA extractions were done, followed by PCR process done using P1/P7 universal primers, gel electrophoresis and amplicon sequencing. For the coconut tree drillings results, the BLAST comparison with existing data in the NCBI database revealed it to be Candidatus phytoplasma palmae strain isolate Tanz08, under gene accession No. GU952107.1. Further phylogenetic analysis using the maximum likelihood method indicated that the strain is closely related to those reported in Tanzania. The CLYD positive samples were identified from Lamu and Kwale counties, with 6 cases from each County. Although there were no positive cases reported in Kilifi and Tana River counties, the presence of the vectors suggests that more studies need to be done on the disease. Further studies should be done on the alternative hosts, varieties prone to the disease, characterization and diversity of the vectors, the incubation period and the host pathogen relationship.

The Clostridium estertheticum complex (CEC) consists of closely related bacterial species that are mostly isolated from meat processing environment. Genome mining studies have recently established CEC as a source of class I bacteriocins. However, up until now, class II bacteriocins have not been reported from CEC. In the present study, we determined the presence of class II bacteriocin biosynthetic clusters in 33 CEC genomes through genome mining followed by bacteriocin production through heterologous expression in Escherichia coli . Six biosynthetic gene clusters belonging to class IIa ( n  = 1), IIb ( n  = 2), IId ( n  = 2) and an undefined class containing three precursor peptides were identified in six different CEC strains. Using molecular biology, we developed dedicated expression vectors for the class IIa bacteriocin, clesteriocin A. Its precursor peptide, CleA, and protease, CleB150, were initially expressed in insoluble form in E. coli . Through a systematic analysis of suitable solubility enhancing protein tags, both CleA and CleB150 were expressed in significant amounts of soluble fractions using tandem tags derived from Small Ubiquitin-like Modifier, superfolder Green fluorescent protein, Maltose binding protein and N-utilization substance. Mature clesteriocin A was obtained following in vitro maturation reactions between the tagged CleA and CleB150. The novel bacteriocin displayed antimicrobial activity against Listeria monocytogenes , which was mediated by the mptC gene. By combining genome mining and molecular biology, we have shown CEC is a source of novel class II bacteriocins that have potential for application as food biopreservatives.

Abstract Multicellular magnetotactic prokaryotes represent a unique group of obligately marine multicellular bacteria known for their ability to navigate along magnetic field lines thanks to ferrimagnetic nanocrystals. To date, two distinct spherical and ellipsoidal morphotypes have been described, typically ranging from 3 to 6 μm in diameter and comprising approximately 50 cells of the same species. Although widespread in highly reduced marine sediments, they are represented by solely three genera clustering into a monophyletic group within the Desulfobacterota. In this study, we report a third morphotype in reduced sediments of the Mediterranean Sea in Carry-le-Rouet, France, that is approximately 30 times more voluminous than any previously described form. Because their large size, we designated these multicellular bacteria as “giant” and explored their cell ultrastructure, ecological niche and physiology using magnetic enrichment and a combination of microscopy techniques and single-consortium genomics. Transmission electron microscopy and confocal microscopy images of several individual consortia revealed that they contain an average of 130 cells, each producing over 100 greigite magnetosomes arranged to optimize the overall magnetic moment. Phylogenomic analyses positioned giant multicellular magnetotactic prokaryotes, together with other morphotypes, in a previously undescribed genus and species within the Candidatus Magnetomoraceae family, named Magnetogigantoglobus mediterraneus. Although genetically divergent with a different ultrastructure, all multicellular magnetotactic prokaryotes seem to rely on sulfate reduction coupled to heterotrophy or autotrophy. We further discuss the significance of these findings in the context of the evolutionary history of multicellularity and magnetotaxis in prokaryotes.

Abstract BACKGROUND The Asian citrus psyllid, Diaphorina citri , vectors Candidatus Liberibacter asiaticus ( C Las) that causes citrus greening disease, which has devastated global citrus production. Current management primarily relies on the application of synthetic chemical insecticides, resulting in the evolution of resistance among D . citri populations. C Las is ingested by D . citri while feeding on infected plants and subsequently interacts with the gut epithelial surface to establish infection. To determine the functional significance of abundant gut surface proteins in D. citri during C Las uptake, we used RNA interference (RNAi) to silence nine key gut surface protein genes. RESULTS Following membrane feeding on double‐stranded RNAs (dsRNAs), transcript levels were reduced by 20–51% in adults and 28–50% in nymphs at 72 h, with higher knockdown efficiencies of 41–63% in adults and 30–81% in nymphs by 120 h. Some dsRNA treatments increased D. citri mortality by approximately 20% over the control treatment, and two treatments reduced honeydew production indicative of reduced feeding consistent with disrupted gut function. Silencing of several individual proteins, including alkaline phosphatase, cadherin, cluster of calcium‐transporting ATPase, croquemort and monocarboxylate transporter, reduced C Las uptake in nymphs and/or adults. CONCLUSION Silencing of abundant gut surface proteins in D. citri limited C Las uptake, establishing a functional basis for RNAi‐mediated suppression of pathogen uptake. While additional studies are needed to determine specific molecular interactions, these results identify gut surface proteins as promising targets for RNAi‐based interventions to reduce C Las uptake by psyllids. © 2026 Society of Chemical Industry.

The prokaryotic generic names Brachymonas Hiraishi et al . 1995 and Bosea Das et al . 1996 are illegitimate because they are later homonyms of the genus names Brachymonas Grassé 1952 (Protozoa, Polymastigidae) and Bosea He and Qian 1979 (a fossil dinoflagellate) [Principle 2 and Rule 51b(4) of the International Code of Nomenclature of Prokaryotes (ICNP)]. We therefore propose the replacement names Allobrachymonas gen. nov., Allobrachymonas chironomi comb. nov., Allobrachymonas denitrificans comb. nov., Allobrachymonas wangyanguii comb. nov., Allobosea gen. nov., Allobosea beijingensis comb. nov., Allobosea caraganae comb. nov., Allobosea eneae comb. nov., Allobosea lathyri comb. nov., Allobosea lupini comb. nov., Allobosea massiliensis comb. nov., Allobosea minatitlanensis comb. nov., Allobosea psychrotolerans comb. nov., Allobosea robiniae comb. nov., Allobosea rubneri comb. nov., Allobosea spartocytisi comb. nov., Allobosea thiooxidans comb. nov., Allobosea vaviloviae comb. nov., Allobosea vestrisii comb. nov. and Alloboseaceae fam. nov.

The prokaryotic genus names Baileyella Wylensek et al . 2021, Lucifera Sánchez-Andrea et al . 2019, and Microvenator Wang et al . 2022 are illegitimate because they are later homonyms of Baileyella Özdikmen 2009 (a fossil member of the Gonyaulacaceae, Gonyaulacales, Dinophyceae), Lucifera Baker 2010 (Keroplaridae, Diptera) and Microvenator Ostrom 1970 (a fossil member of the Caetagnatidae, Saurichia, Reptilia), respectively [Principle 2 and Rule 51b(5) of the International Code of Nomenclature of Prokaryotes (ICNP)]. We therefore propose the replacement names Allobaileyella gen. nov., Allobaileyella intestinalis comb. nov., Allolucifera gen. nov., Allolucifera butyrica comb. nov., Allomicrovenator gen. nov., Allomicrovenator marinus comb. nov. and Allomicrovenatoraceae fam. nov.