Biology subjects

Alvarez, A. M.

Publications and source records attributed to Alvarez, A. M..

12 recordsLinked to original sources

bioRxiv2025

Description of two novel non-pathogenic tomato-associated Clavibacter species: Clavibacter seminis sp. nov. and Clavibacter quasicaliforniensis sp. nov.

The Clavibacter genus is currently split into ten species, including C. michiganensis, C. nebraskensis, C. capsici, C. sepedonicus, C. tessellarius, C. insidiosus, C. californiensis, C. phaseoli, C. zhangzhiyongii, and the newly described C. lycopersici. These bacterial species have been isolated from different hosts, and some members are reported as non-pathogenic. In this study, we have sequenced and reported high-quality complete genomes of three new Clavibacter strains A6099T, A4868, and A6308 isolated from tomato using Oxford nanopore MinION and Illumina NovaSeq sequencing platforms. In addition, the taxonomy position of other three Clavibacter strains from the NCBI GenBank database LMG 26808, CFBP 7493, and VKM Ac-22542 were assessed and properly defined. Application of different in silico approaches such as calculation of the average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), alignment coverage (AP), multi-locus sequence analysis (MLSA) of eight housekeeping genes atpD, dnaA, dnaK, pgi, gyrB, ppk, recA and rpoB, and a phylogenomic analysis of 808 core genes of 97 Clavibacter strains, including the three sequenced novel Clavibacter strains, led us to differentiate two novel clades within the Clavibacter genus that are closely related to C. michiganensis and C. californiensis. The ANI and dDDH values were lower than the 96 and 70% cut-off values for species delineation, respectively; likewise, the phylogenies showed a clear differentiation of these two novel clades with respect to the other Clavibacter species. Therefore, we suggest establishing two new species to correctly classify these two novel clades, for which we propose the species names: Clavibacter seminis sp. nov. formed by the type strain A6099T, LMG 26808 and CFBP 7493, and Clavibacter quasicaliforniensis sp. nov., composed of the type strain A4868T, A6308, and CFBP 7493. The two new species were non-pathogenic on tomato seedlings, their isolation host, which correlated with the absence of the major virulence-associated genes determined in our comparative genomics analyses.

plant biology↗

bioRxiv2024

Development and Validation of Genome-Informed and Multigene-based qPCR and LAMP Assays for Accurate Detection of Dickeya solani: A Critical Quarantine Pathogen Threatening Potato Industry

Dickeya solani, one of the most aggressive pectinolytic phytopathogens, causes blackleg disease in potatoes, resulting in significant economic losses and adversely impacting one of the worlds most important food crops. The diagnostics methods are critical in monitoring the latent infection for international trade of potato seed-tubers and in implementation of control strategies. Our study employed a whole-genome comparative approach, identifying unique target gene loci (LysR and TetR family of transcriptional regulators gene regions), design loop-mediated isothermal amplification (LAMP) and a multi-gene-based multiplex TaqMan qPCR assays for specific detection and differentiation of D. solani. Both methods underwent meticulous validation with extensive inclusivity and exclusivity panels, exhibiting 100% accuracy and no false positives or negatives. The LAMP method demonstrated the detection limit of 100 fg and 1 CFU per reaction using pure genomic DNA and crude bacterial cell lysate, respectively. The qPCR detection limit was 1 pg, 100 fg and 10 fg with Quadplex, triplex and singleplex, respectively. None of the assay showed any inhibitory effect after adding host DNA (in qPCR) or crude lysate (in LAMP). The assays proved robust and reproducible in detecting the target pathogen in infected samples, with the LAMP assay being field-deployable due to its simplicity and rapid results acquisition within approximately 8.92 minutes. The reproducibility was confirmed by performing the assay in two independent laboratories. These developed assays offer a robust, rapid, and reliable solution for routine testing, with applications in phytosanitary inspection and epidemiological studies. IMPORTANCEDickeya solani, one of the most aggressive soft rots causing-bacteria and a quarantine pathogen, poses a severe threat to food security by causing substantial economic losses to potato industry. Accurate and timely detection of this bacteria is vital for monitoring latent infections, particularly for international trade of potato seed tubers, and for implementing effective control strategies. In this research we have developed a LAMP and a multi-gene-based multiplex TaqMan qPCR assays for specific detection of D. solani. These assays, characterized by their precision, rapidity, and robustness, are crucial for distinguishing D. solani from related species. Offering unparalleled sensitivity and specificity, these assays are indispensable for phytosanitary inspection and epidemiological monitoring, providing a powerful tool for management of this threatening pathogen.

microbiology↗

bioRxiv2023

Three new species, Xanthomonas hawaiiensis sp. nov., Stenotrophomonas aracearum sp. nov., and Stenotrophomonas oahuensis sp. nov., isolated from Araceae family

Xanthomonas and Stenotrophomonas are closely related genera in the family Lysobacteraceae. In our previous study of aroid-associated bacterial strains, most strains isolated from anthurium, and other aroids were reclassified as X. phaseoli and other Xanthomonas species. However, two strains from Spathiphyllum and Colocasia were phylogenetically distant from other strains in the Xanthomonas clade and two anthurium strains clustered within the Stenotrophomonas clade. Phylogenetic trees based on 16S rRNA and nine housekeeping genes placed the former strains with type strain of X. sacchari from sugarcane and the latter strains with type strain of S. bentonitica from bentonite. In pairwise comparisons with type strains, the overall genomic relatedness indices required delineation of new species; digital DNA-DNA hybridization and average nucleotide identity values were lower than 70% and 95%, respectively. Hence, three new species are proposed: S. aracearum sp. nov. and S. oahuensis sp. nov. for two anthurium strains, and X. hawaiiensis sp. nov. for the spathiphyllum and colocasia strains. The genome size of X. hawaiiensis sp. nov. is [~]4.88 Mbp and higher than S. aracearum sp. nov. (4.33 Mbp) and S. oahuensis sp. nov. (4.68 Mbp). Pan and core-genome analyses revealed 426 and 576 core genes present in 40 xanthomonads and 25 stenotrophomonads, respectively. The average number of unique genes in Stenotrophomonas spp. was higher than in Xanthomonas spp. implying higher genetic diversity in Stenotrophomonas.

microbiology↗

bioRxiv2022

Exploring Taxonomic and Functional Microbiome of Hawaiian Stream and Spring Irrigation Water Systems Using Illumina and Oxford Nanopore Sequencing Platforms

Irrigation water is a potential source of contamination that carries plant and foodborne human pathogens and provides a niche for survival and proliferation of microbes in agricultural settings. This project investigated bacterial communities and their functions in the irrigation water from wetland taro farms on Oahu, Hawaii using different DNA sequencing platforms. Irrigation water samples (stream, spring, and tank stored water) were collected from North, East, and West sides of Oahu and subjected to high quality DNA isolation, library preparation and sequencing of the V3-V4 region, full length 16S rRNA, and shotgun metagenome sequencing using Illumina iSeq100, Oxford Nanopore MinION and Illumina NovaSeq, respectively. Illumina reads provided the most comprehensive taxonomic classification at the phylum level where Proteobacteria was identified as the most abundant phyla in river stream source and associated wet taro field water samples. Cyanobacteria was also a dominant phylum from tank and spring water, whereas Bacteroidetes were most abundant in wetland taro fields irrigated with spring water. However, over 50% of the valid short amplicon reads remained unclassified and inconclusive at the species level. Whereas samples sequenced for full length 16S rRNA and shotgun metagenome, clearly illustrated that Oxford Nanopore MinION is a better choice to classify the microbes to the genus and species levels. In terms of functional analyses, only 12% of the genes were shared by two consortia. Total 95 antibiotic resistant genes (ARGs) were detected with variable relative abundance. Description of microbial communities and their functions are essential for the development of better water management strategies to produce safer fresh produce and to protect plant, animal, human and environmental health. This project identified analytical tools to study microbiome of irrigation water.

microbiology↗

bioRxiv2022

Pectobacterium colocasium sp. nov. isolated from taro (Colocasia esculenta)

Pectobacterium, agenus comprising gram-negative, pectinolytic phytopathogens, is responsible for economic losses in a wide host range of plants. In this study, the bacterial strains PL152T and PL155 were isolated from taro corms in Hawaii in 2018, and characterized using genomic and biochemical assays. The Next Generation Sequencing technologies, Oxford Nanopore MinION and Illumina NovaSeq, were used for whole genome sequencing of the PL152T strain. Short and long reads were assembled using the Unicycler tool accessible at the bioinformatic resource center, and PATRIC (PathoSystems Resource Integration Center) was used to generate a more accurate and reliable "hybrid" assembly. The 16S rRNA analysis of PL152T with type strains of other known Pectobacterium species showed a close relationship with P. fontis. Multi-locus sequence analysis using nine housekeeping genes (dnaA, gapA, gyrB, recA, dnaN, rpoS, mdh, rpoA and dnaK) differentiated strain PL152T from other species of Pectobacterium and formed a unique and well-defined clade. The concurrent results of average nucleotide identity (ANI) and digital DNA-DNA hybridization, with calculated values lower than 95 and 70%, respectively, supported the delineation of a novel bacterial species. Here, we proposed Pectobacterium colocasium, strain PL152T (=ICMP 24362T; LMG 32536 T) and PL155 as a novel species in the genus Pectobacterium. 1.5 RepositoriesCP091064; MZ542535 - MZ542540; OM457660

microbiology↗

bioRxiv2022

Elevation of Clavibacter michiganensis subsp. californiensis to species level as Clavibacter californiensis sp. nov., merging and re-classification of Clavibacter michiganensis subsp. chilensis and Clavibacter michiganensis subsp. phaseoli as Clavibacter chilensis sp. nov. based on complete genome in-silico analyses

The Gram-positive Clavibacter genus is currently divided into seven species (C. michiganensis, C. nebraskensis, C. capsici, C. sepedonicus, C. tessellarius, C. insidiosus and C. zhangzhiyongii) and three subspecies (C. michiganensis subsp. californiensis, C. michiganensis subsp. chilensis and C. michiganensis subsp. phaseoli). Recent studies have indicated that the taxonomic rank of the subspecies must be re-evaluated. In this research, we assessed the taxonomy position of the three C. michiganensis subspecies and clarified the taxonomic nomenclature of other 75 Clavibacter strains. The complete genomes of the type strains of the three Clavibacter subspecies, type strain of C. tessellarius and C. nebraskensis A6096 were sequenced using PacBio RSII technology. Application of whole-genome-based computational approaches such as average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), multi-locus sequence analysis (MLSA) of seven housekeeping genes (acnA, atpD, bipA, icdA, mtlD, recA and rpoB), phylogenomic tree reconstructed from 1,028 core genes, and ANI-based phylogeny pinpointed conclusive evidence to raise C. michiganensis subsp. californiensis to the species status. These results led us to propose the establishment of C. californiensis sp. nov. as a species with its type strain C55 (=CFBP 8216=ATCC BAA-2691). Moreover, the orthologous and in-silico dot plot analyses, along with the aforementioned bioinformatic strategies, revealed a high degree of homology between C. michiganensis subsp. chilensis and C. michiganensis subsp. phaseoli. Based on these outcomes, we proposed to combine both subspecies into a single taxon and elevate its rank to the species level as C. chilensis sp. nov., with ZUM3936 (= ATCC BAA-2690 = CFBP 8217) as the type strain.

microbiology↗

bioRxiv2022

Dickeya colocasiae sp. nov. isolated from wetland taro, Colocasia esculentum

Bacterial pathogens identified as Dickeya sp. have recently been associated with a corm rot of wetland taro on Oahu, Hawaii, but the species designation of these strains was unclear. A Gram-negative, pectinolytic bacterial strain PL65T isolated from an infected taro corm was subjected to polyphasic analysis to determine its genomic and phenotypic characteristics. Multi-locus sequence analyses (MLSA) based on five housekeeping genes (dnaA, gapA, gyrB, atpD, and purA) revealed that Dickeya zeae and D. oryzae, were the closest relatives. Phylogenetic analysis based on 463 core gene sequences clearly showed two potentially new species within Dickeya oryzae. In silico DNA- DNA hybridization value of strain PL65T with 12 Type strains of Dickeya species was <68%. Average nucleotide identity (ANI) analysis revealed that PL65T was at the margin of the species delineation cut-off values with a 96% ANI value. The metabolic profile of strain PL65T using BIOLOG differentiated it from the type strains of all other known species of Dickeya. Based on the results of genome-to-genome comparisons and phenotypic data presented in this report, we propose establishment of a new species, Dickeya colocasiae sp. nov. with strain PL65T as the type strain (ICMP 24361T).

microbiology↗

bioRxiv2021

Metabolic dysregulation induces impaired lymphocyte memory formation during severe SARS-CoV-2 infection

Cellular metabolic dysregulation is a consequence of COVID-19 infection that is a key determinant of disease severity. To understand the mechanisms underlying these cellular changes, we performed high-dimensional immune cell profiling of PBMCs from COVID-19-infected patients, in combination with single cell transcriptomic analysis of COVID-19 BALFs. Hypoxia, a hallmark of COVID-19 ARDS, was found to elicit a global metabolic reprogramming in effector lymphocytes. In response to oxygen and nutrient-deprived microenvironments, these cells shift from aerobic respiration to increase their dependence on anaerobic processes including glycolysis, mitophagy, and glutaminolysis to fulfill their bioenergetic demands. We also demonstrate metabolic dysregulation of ciliated lung epithelial cells is linked to significant increase of proinflammatory cytokine secretion and upregulation of HLA class 1 machinery. Augmented HLA class-1 antigen stimulation by epithelial cells leads to cellular exhaustion of metabolically dysregulated CD8 and NK cells, impairing their memory cell differentiation. Unsupervised clustering techniques revealed multiple distinct, differentially abundant CD8 and NK memory cell states that are marked by high glycolytic flux, mitochondrial dysfunction, and cellular exhaustion, further highlighting the connection between disrupted metabolism and impaired memory cell function in COVID-19. Our findings provide novel insight on how SARS-CoV-2 infection affects host immunometabolism and anti-viral response during COVID-19. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/471421v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@18bff7borg.highwire.dtl.DTLVardef@31f46borg.highwire.dtl.DTLVardef@1a5ad50org.highwire.dtl.DTLVardef@1577a0_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIHypoxia and anaerobic glycolysis drive CD8, NK, NKT dysfunction C_LIO_LIHypoxia and anaerobic glycolysis impair memory differentiation in CD8 and NK cells C_LIO_LIHypoxia and anaerobic glycolysis cause mitochondrial dysfunction in CD8, NK, NKT cells C_LI

immunology↗

bioRxiv2021

Genomic and phenotypic biology of novel strains of Dickeya zeae isolated from pineapple and taro in Hawaii: insights into genome plasticity, pathogenicity, and virulence determinants

Dickeya zeae, a bacterial plant pathogen in the family Pectobacteriaceae, is responsible for a wide range of diseases on potato, maize, rice, banana, pineapple, taro and ornamentals and significantly reduces crop production; D. zeae causes soft rot of taro (Colocasia esculenta) and heart rot of pineapple (Ananas comosus). In this study, we used Pacific Biosciences to sequence two high quality complete genomes of novel strains of D. zeae: PL65 (size - 4.74997 MB; depth - 701; GC - 53.3%) and A5410 (size - 4.7792 MB; depth - 558; GC - 53.6%) isolated from economically important Hawaiian crops, taro and pineapple, respectively. Additional complete genomes of D. zeae representing two additional hosts (rice and banana), and other species for taxonomic comparison, were retrieved from the NCBI GenBank genome database. The genomic analyses indicated truncated type III and IV secretion systems (T3SS and T4SS) in the taro strain, which only harbors 1 and 2 genes of T3SS and T4SS, respectively, and showed high heterogeneity in the type VI secretion system. Unlike the EC1 strain, neither the PL65 nor the A5410 genome harbors the zeamine biosynthesis gene cluster, which plays a key role in bacterial virulence. The ANI and dDDH percentages between the two genomes were 94.47 and 57.00, respectively. In this study, we compared major virulence factors (plant cell wall-degrading extracellular enzymes and protease) produced by D. zeae strains and virulence ability on taro corms and pineapple. Both strains produced protease, pectate lyases and cellulases but no significant quantitative differences were observed (p>0.05) among the strains. All the strains produced symptoms on taro corms and pineapple leaves. Strain PL65 developed symptoms faster than the others. Our study highlights genetic constituents of pathogenicity determinants and genomic heterogeneity that will help understand the virulence mechanisms and aggressiveness of this plant pathogen.

genomics↗

bioRxiv2020

Multiplex recombinase polymerase amplification (RPA) assay developed using unique genomic regions and coupled with a lateral flow device for rapid on-site detection of genus Clavibacter and C. nebraskensis

Clavibacter is an agriculturally important bacterial genus comprising nine host-specific species/subspecies including C. nebraskensis (Cn), which causes Gosss wilt and blight of maize. A robust, simple, and field-deployable method is required to specifically detect Cn in infected plants and distinguish it from other Clavibacter species for quarantine purposes and timely disease management. A multiplex Recombinase Polymerase Amplification (RPA) coupled with a Lateral Flow Device (LFD) was developed for sensitive and rapid detection of Clavibacter and Cn directly from infected host. Unique and conserved genomic regions, the ABC transporter ATP-binding protein CDS/ABC-transporter permease and the MFS transporter gene, were used to design primers/probes for specific detection of genus Clavibacter and Cn, respectively. The assay was evaluated using 52 strains, representing all nine species/subspecies of Clavibacter, other closely related bacterial species, and naturally- and artificially-infected plant samples; no false positives or negatives were detected. The RPA reactions were also incubated in a closed hand at body temperature; results were again specific. The assay does not require DNA isolation and can be directly performed using host sap. The detection limit of 10 pg and 100 fg was determined for Clavibacter- and Cn-specific primers/probes, respectively. The detection limit for Cn-specific primer/probe set was decreased to 1,000 fg when 1 {micro}L of host sap was added into the RPA reaction containing 10-fold serially diluted genomic DNA; though no effect was observed on Clavibacter-specific primer/probe set. The assay is accurate and has applications at point-of-need diagnostics. This is the first multiplex RPA for any plant pathogen. IMPORTANCEClavibacter species are prevalent worldwide as have the potential to result in systemic infection. In the past, detection attempts have relied on both molecular- and immunological-based assays; however, current detection methods are time consuming and laborious. Field-deployable tests are desirable to identify potential samples infected with Clavibacter species. This study demonstrates that the field-deployable isothermal multi-target recombinase polymerase amplification can be performed for the simultaneous detection of the genus Clavibacter in general (all species), and C. nebraskensis, in particular, without specialized equipment. Additionally, the multiplex RPA coupled with a LFD may confer the benefits of faster detection and discrimination of Clavibacter species that affect critical regions susceptible to infection. This user-friendly format offers a flexible assay to complement both nucleic acid amplification and novel diagnosis methods without the need for DNA purification; this assay may serve as a point-of-reference for developing multiplex RPA assay for other plant pathogens.

microbiology↗

bioRxiv2019

Comparative genomics reveals signature regions used to develop a robust and sensitive multiplex TaqMan real-time qPCR assay to detect the genus Dickeya and Dickeya dianthicola

AimsDickeya species are high consequence plant pathogenic bacteria listed among the quarantine pathogens of the European Union; associated with potato disease outbreaks and subsequent economic losses worldwide. Early, accurate, and reliable detection of Dickeya spp. is needed to prevent establishment and further dissemination of this pathogen. Therefore, a multiplex TaqMan qPCR was developed for sensitive detection of Dickeya spp. and specifically, D. dianthicola. Methods and ResultsA signature genomic region for the genus Dickeya (mglA/mglC) and unique genomic region for D. dianthicola (alcohol dehydrogenase) were identified using a whole genome based comparative genomics approach. The developed multiplex TaqMan qPCR was validated using extensive inclusivity and exclusivity panels, and naturally/artificially infected samples to confirm broad range detection capability and specificity. Both sensitivity and spiked assays showed detection limit of 10 fg DNA. ConclusionThe developed multiplex assay is sensitive and reliable to detect Dickeya spp. and D. dianthicola with no false positives or false negatives. It was able to detect mixed infection from naturally and artificially infected plant materials. Significance and ImpactThe developed assay will serve as a practical tool for screening of propagative material, monitoring the presence and distribution, and quantification of target pathogens in a breeding program. The assay also has applications in routine diagnostics, biosecurity and microbial forensics.

plant biology↗

bioRxiv2019

Synergetic effect of non-complementary 5’ AT-rich sequences on the development of a multiplex TaqMan real-time PCR for specific and robust detection of Clavibacter michiganensis and C. michiganensis subsp. nebraskensis

Clavibacter is an agriculturally important genus comprising a single species, Clavibacter michiganensis, and multiple subspecies, including, C. michiganensis subsp. nebraskensis which causes Gosss wilt/blight of corn and accounts for high yield losses - listed among the five most significant diseases of corn in the United States of America. Our research objective was to develop a robust and rapid multiplex TaqMan real-time PCR (qPCR) to detect C. michiganensis in general and C. michiganensis subsp. nebraskensis with enhanced reliability and accuracy by adding non-complementary AT sequences to the 5 end of the forward and reverse primers. Comparative genomic analyses were performed to identify unique and conserved gene regions for primer and probe design. The unique genomic regions, ABC transporter ATP-binding protein CDS/ABC-transporter permease and MFS transporter were determined for specific detection of C. michiganensis and C. m. subsp. nebraskensis, respectively. The AT-rich sequences at the 5 position of the primers enhanced the reaction efficiency and sensitivity of rapid qPCR cycling; the reliability, accuracy and high efficiency of the developed assay was confirmed after testing with 59 strains from inclusivity and exclusivity panels - no false positives or false negatives were detected. The assays were also validated through naturally and artificially infected corn plant samples; all samples were detected for C. michiganensis and C. m. subsp. nebraskensis with 100% accuracy. The assay with 5 AT-rich sequences detected up to 10- and 100-fg of C. michiganensis and C. michiganensis subsp. nebraskensis genome targets, respectively. No adverse effect was observed when sensitivity assays were spiked with host genomic DNA. Addition of 5 AT rich sequences enhanced the qPCR reaction efficiency from 0.82 (M = -3.83) and 0.91 (M = -3.54) to 1.04 (with optimum slope value; M = -3.23) for both C. michiganensis and C. michiganensis subsp. nebraskensis, respectively; a increase of 10-fold sensitivity was also obtained with C. michiganensis primer set. The methodology proposed here can be used to optimize the reaction efficiency and to harmonize the diagnostic protocols which have prodigious applications in routine diagnostics, biosecurity and microbial forensics.

plant biology↗