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A novel Gram-negative, rod-shaped and motile bacterial strain, designated strain M36 T , was isolated from a culture of a bloom-forming cyanobacterium, Microcystis sp., collected from a eutrophic lake in Korea. Its taxonomic position was investigated by using a polyphasic taxonomic approach. The isolate was found to grow aerobically at 15–42 °C (optimum 25 °C), pH 7.0–11.0 (optimum pH 8.0) and in the presence of 0–1.0% (w/v) NaCl (optimum 0% NaCl) on R2A medium. The phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain M36 T is closely related to Acidovorax anthurii DSM 16745 T (98.1%), Acidovorax konjaci DSM 7481 T (97.7%) and Acidovorax avenae DSM 7227 T (97.0%) and also formed a clear phylogenetic lineage with other Acidovorax species. DNA–DNA relatedness between strain M36 T and the closely related species of the genus Acidovorax was <30%. The major fatty acid components identified included summed feature 3 (C 16:1 ω 7 c and/or C 16:1 ω 6 c ), C 16:0 and summed feature 8 (C 18:0 ω 7 c and/or C 18:0 ω 6 c ). The DNA G+C content of strain M36 T was determined to be 66.8 mol%. Based on above polyphasic evidence, strain M36 T is concluded to represent a new species of genus Acidovorax , for which the name Acidovorax lacteus sp. nov. is proposed. The type strain is M36 T (=KCTC 52220 T  = JCM 31890 T ).

Phages utilize lysis systems to allow the release of newly assembled viral particles that kill the bacterial host. This is also the case for phage AP1, which infects the rice pathogen Acidovorax oryzae. However, how lysis occurs on a molecular level is currently unknown. We performed in silico bioinformatics analyses, which indicated that the lysis cassette contains a holin (HolAP) and endolysin (LysAP), which are encoded by two adjacent genes. Recombinant expression of LysAP caused Escherichia coli lysis, while HolAP arrested growth. Co-expression of both proteins resulted in enhanced lysis activity compared to the individual proteins alone. Interestingly, LysAP contains a C-terminal region transmembrane domain, which is different from most known endolysins where a N-terminal hydrophobic region is found, with the potential to insert into the membrane. We show that the C-terminal transmembrane domain is crucial for protein localization and bacterial lysis in phage AP1. Our study characterizes the new phage lysis cassette and the mechanism to induce cell disruption, giving new insight in the understanding of phage life cycles.

Summary The cucurbit pathogenic bacterium Acidovorax citrulli requires a functional type III secretion system (T3SS) for pathogenicity. In this bacterium, as with Xanthomonas and Ralstonia spp., an AraC‐type transcriptional regulator, HrpX, regulates expression of genes encoding T3SS components and type III‐secreted effectors (T3Es). The annotation of a sequenced A. citrulli strain revealed 11 T3E genes. Assuming that this could be an underestimation, we aimed to uncover the T3E arsenal of the A. citrulli model strain, M6. Thorough sequence analysis revealed 51 M6 genes whose products are similar to known T3Es. Furthermore, we combined machine learning and transcriptomics to identify novel T3Es. The machine‐learning approach ranked all A. citrulli M6 genes according to their propensity to encode T3Es. RNA‐Seq revealed differential gene expression between wild‐type M6 and a mutant defective in HrpX: 159 and 28 genes showed significantly reduced and increased expression in the mutant relative to wild‐type M6, respectively. Data combined from these approaches led to the identification of seven novel T3E candidates that were further validated using a T3SS‐dependent translocation assay. These T3E genes encode hypothetical proteins that seem to be restricted to plant pathogenic Acidovorax species. Transient expression in Nicotiana benthamiana revealed that two of these T3Es localize to the cell nucleus and one interacts with the endoplasmic reticulum. This study places A. citrulli among the ‘richest’ bacterial pathogens in terms of T3E cargo. It also revealed novel T3Es that appear to be involved in the pathoadaptive evolution of plant pathogenic Acidovorax species.

Background Lung cancer is the leading cancer diagnosis worldwide and the number one cause of cancer deaths. Exposure to cigarette smoke, the primary risk factor in lung cancer, reduces epithelial barrier integrity and increases susceptibility to infections. Herein, we hypothesize that somatic mutations together with cigarette smoke generate a dysbiotic microbiota that is associated with lung carcinogenesis. Using lung tissue from 33 controls and 143 cancer cases, we conduct 16S ribosomal RNA (rRNA) bacterial gene sequencing, with RNA-sequencing data from lung cancer cases in The Cancer Genome Atlas serving as the validation cohort. Results Overall, we demonstrate a lower alpha diversity in normal lung as compared to non-tumor adjacent or tumor tissue. In squamous cell carcinoma specifically, a separate group of taxa are identified, in which Acidovorax is enriched in smokers. Acidovorax temporans is identified within tumor sections by fluorescent in situ hybridization and confirmed by two separate 16S rRNA strategies. Further, these taxa, including Acidovorax , exhibit higher abundance among the subset of squamous cell carcinoma cases with TP53 mutations, an association not seen in adenocarcinomas. Conclusions The results of this comprehensive study show both microbiome-gene and microbiome-exposure interactions in squamous cell carcinoma lung cancer tissue. Specifically, tumors harboring TP53 mutations, which can impair epithelial function, have a unique bacterial consortium that is higher in relative abundance in smoking-associated tumors of this type. Given the significant need for clinical diagnostic tools in lung cancer, this study may provide novel biomarkers for early detection.

How cells determine where to assemble a macromolecular complex is a fundamental question in biology since the localization of these complexes is directly linked to functions. In bacteria, the type VI secretion system (T6SS) relies on effective positioning to target competitor and host cells in contact-dependent interactions. This study identifies a PpkA-TssW-Fha axis that orchestrates T6SS localization and activation through membrane anchoring and liquid-liquid phase separation at the inner membrane interface. These new insights can help us not only better understand how the T6SS functions but also better design T6SS-based solutions for therapeutic targeting of drug-resistant and T6SS-susceptible bacterial and fungal pathogens.

Pathogenesis-related protein 10 (PR10) family genes play a crucial role in plant defense against various stressors. However, gene member and function identification of PR10 family in sugarcane remain largely unexplored. This study systematically identified and characterized this family genes in Saccharum spontaneum genome as well as their transcriptional expression in two sugarcane cultivars in response to infection by pathogenic bacteria Xanthomonas albilineans ( Xa ) and Acidovorax avenae subsp. avenae ( Aaa ) and foliar application of exogenous salicylic acid (SA). A total of 24 SsPR10 family genes were identified and categorized into two subfamilies, i.e., IPR10 ( SsIPR10-1–14 ) and NCS ( SsNCS-1–10 ). Six and two sets of SsPR10 underwent tandem and fragmental duplication events, respectively. RNA sequencing dataset and quantitative RT-PCR assay uncovered that ShIPR10-1/2/4/7/11/12 and ShNCS-8 genes were dramatically upregulated with increases of 3.2–107.2-fold in LCP85-384 (resistant to leaf scald), while they were slightly upregulated with increases of 1.26–7.1-fold in ROC20 (susceptible to leaf scald) for 24–72 h post inoculation under Xa infection. ShIPR10-1/7/12 and ShNCS-8 were significantly upregulated in both cultivars triggered by Aaa infection with increases of 2.4–21.0-fold. Under exogenous salicylic acid treatment, ShIPR10-1/2/4/7/11/12 were remarkably upregulated by 3.6–6.1-fold in LCP85-384 at 12 h post treatment (hpt) but were downregulated by 81.3% in ROC20 at 24 hpt, as compared to the control 0 hpt. In addition, ShNPR1 and ShPR1 involved in the SA signal transduction pathway displayed positive roles in sugarcane under both bacterial attacks and SA treatment. Collectively, our data provide important genetic resources for improving sugarcane tolerance to pathogenic bacterial stress and disease-resistance breeding in sugarcane for food security.

A novel strain K-4-16T was isolated from forest soil of Namsan Mountain, Seoul, South Korea, and was taxonomically characterized by a polyphasic approach. Strain K-4-16T was observed to be a Gram-staining negative, grayish white-coloured, motile with peritrichous flagella, and rod shaped bacterium. It was able to grow at 15–45 °C, at pH 4.5–10.5, and at 0–4% (w/v) NaCl concentration. Based on the 16S rRNA gene sequence analysis, strain K-4-16T belongs to the genus Acidovorax and is closely related to Acidovorax anthurii CFBP 3232T (98.3% sequence identity), Acidovorax konjaci K2T (97.9% sequence identity), Acidovorax valerianellae CFBP 4730T (97.8% sequence identity), and Acidovorax caeni R-24608T (97.8% sequence identity). The only respiratory quinone was ubiquinone-8. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. The predominant fatty acids of strain K-4-16T were summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0, and summed feature 8 (C18:1ω7c and/or C18:1ω6c). The genomic DNA G+C content of this novel strain was 64.7 mol%. The DNA–DNA relatedness between strain K-4-16T and its reference strains were below the threshold value of 70%. The morphological, physiological, chemotaxonomic, and phylogenetic analyses clearly distinguished this strain from its close phylogenetic neighbors. Thus, strain K-4-16T represents a novel species of the genus Acidovorax, for which the name Acidovorax monticola sp. nov. is proposed. The type strain is K-4-16T (= KEMB 9005-570T = KACC 19171T = NBRC 113141T).

Sugarcane is an important tropical crop mainly cultivated to produce ethanol and sugar. Crop productivity is negatively affected by Acidovorax avenae subsp avenae (Aaa), which causes the red stripe disease. Little is known about the molecular mechanisms triggered in response to the infection. We have investigated the molecular mechanism activated in sugarcane using a RNA-seq approach. We have produced a de novo transcriptome assembly (TR7) from sugarcane RNA-seq libraries submitted to drought and infection with Aaa. Together, these libraries present 247 million of raw reads and resulted in 168,767 reference transcripts. Mapping in TR7 of reads obtained from infected libraries, revealed 798 differentially expressed transcripts, of which 723 were annotated, corresponding to 467 genes. GO and KEGG enrichment analysis showed that several metabolic pathways, such as code for proteins response to stress, metabolism of carbohydrates, processes of transcription and translation of proteins, amino acid metabolism and biosynthesis of secondary metabolites were significantly regulated in sugarcane. Differential analysis revealed that genes in the biosynthetic pathways of ET and JA PRRs, oxidative burst genes, NBS-LRR genes, cell wall fortification genes, SAR induced genes and pathogenesis-related genes (PR) were upregulated. In addition, 20 genes were validated by RT-qPCR. Together, these data contribute to a better understanding of the molecular mechanisms triggered by the Aaa in sugarcane and opens the opportunity for the development of molecular markers associated with disease tolerance in breeding programs.

Sugarcane ( Saccharum spp.) is an important cash crop for production of sugar and bioethanol. Red stripe caused by Acidovorax avenae subsp. avenae ( Aaa ) is a disease that occurs in numerous sugarcane-growing regions worldwide. In this study, 17 strains of Aaa were isolated from 13 symptomatic leaf samples in China. Nine of these strains produced white-cream colonies on nutrient agar medium while the other eight produced yellow colonies. In pairwise sequence comparisons of the 16S-23S rRNA internally transcribed spacer (ITS), the 17 strains had 98.4-100% nucleotide identity among each other and 98.2-99.5% identity with the reference strain of Aaa (ATCC 19860). Three RFLP patterns based on this ITS sequence were also found among the strains of Aaa obtained in this study. Multilocus sequence typing (MLST) based on five housekeeping genes ( ugp B, pil T, lep A, trp B, and glt A) revealed that the strains of Aaa from sugarcane in China and a strain of Aaa (30179) isolated from sorghum in Brazil formed a unique evolutionary subclade. Twenty-four additional strains of Aaa from sugarcane in Argentina and from other crops worldwide were distributed in two other and separate subclades, suggesting that strains of A. avenae from sugarcane are clonal populations with local specificities. Two strains of Aaa from China (CNGX08 forming white-cream colored colonies and CNGD05 forming yellow colonies) induced severe symptoms of red stripe in sugarcane varieties LC07-150 and ZZ8 but differed based on disease incidence in two separate inoculation experiments. Infected plants also exhibited increased salicylic acid (SA) content and transcript expression of gene PR-1 , indicating that the SA-mediated signal pathway is involved in the response to infection by Aaa . Consequently, red stripe of sugarcane in China is caused by genetically different strains of Aaa and at least two morphological variants. The impact of these independent variations on epidemics of red stripe remains to be investigated.

Acidovorax citrulli, the gram-negative bacteria that causes bacterial fruit blotch (BFB), has been responsible for huge worldwide economic losses in watermelon and melon production since 1980. No commercial cultivar resistant to BFB has been reported. Of the two reported genotypes of A. citrulli, genotype I is the main causal agent of BFB in melon and genotype II causes disease in watermelon. After the isolation of the first bacteriophage against A. citrulli (ACP17), efforts have been made to isolate bacteriophages with wider host ranges by collecting samples from watermelon, pumpkin, and cucumber. The newly isolated phage ACPWH, belonging to the Siphoviridae family, has a head size of 60 ± 5 nm and tail size of 180 ± 5 nm, and can infect 39 out of 42 A. citrulli strains. ACPWH has genome size of 42,499 and GC content of 64.44%. Coating watermelon seeds with bacteriophage ACPWH before soil inoculation with A. citrulli resulted in 96% germination and survival, compared to 13% germination of uncoated control seeds. These results suggest that phage ACPWH may be an effective and low-cost biocontrol agent against BFB.