Advancement of DNA sequencing technology allows the routine use of genome sequences in the various fields of microbiology. The information held in genome sequences proved to provide objective and ...reliable means in the taxonomy of prokaryotes. Here, we describe the minimal standards for the quality of genome sequences and how they can be applied for taxonomic purposes.
Until around 1990, most multigene families were thought to be subject to concerted evolution, in which all member genes of a family evolve as a unit in concert. However, phylogenetic analysis of MHC ...and other immune system genes showed a quite different evolutionary pattern, and a new model called birth-and-death evolution was proposed. In this model, new genes are created by gene duplication and some duplicate genes stay in the genome for a long time, whereas others are inactivated or deleted from the genome. Later investigations have shown that most non-rRNA genes including highly conserved histone or ubiquitin genes are subject to this type of evolution. However, the controversy over the two models is still continuing because the distinction between the two models becomes difficult when sequence differences are small. Unlike concerted evolution, the model of birth-and-death evolution can give some insights into the origins of new genetic systems or new phenotypic characters.
Iturins and closely related lipopeptides constitute a family of antifungal compounds known as iturinic lipopeptides that are produced by species in the
group. The compounds that comprise the family ...are: iturin, bacillomycin D, bacillomycin F, bacillomycin L, mycosubtilin, and mojavensin. These lipopeptides are prominent in many
strains that have been commercialized as biological control agents against fungal plant pathogens and as plant growth promoters. The compounds are cyclic heptapeptides with a variable length alkyl sidechain, which confers surface activity properties resulting in an affinity for fungal membranes. Above a certain concentration, enough molecules enter the fungal cell membrane to create a pore in the cell wall, which leads to loss of cell contents and cell death. This study identified 330 iturinic lipopeptide clusters in publicly available genomes from the
species group. The clusters were subsequently assigned into distinguishable types on the basis of their unique amino acid sequences and then verified by HPLC MS/MS analysis. The results show some lipopeptides are only produced by one species, whereas certain others can produce up to three. In addition, four species previously not known to produce iturinic lipopeptides were identified. The distribution of these compounds among the
group species suggests that they play an important role in their speciation and evolution.
The composition and structure of microbial communities that inhabit the mosquito midguts are poorly understood despite their well-documented potential to impede pathogen transmission.
We used MiSeq ...sequencing of the 16S rRNA gene to characterize the bacterial communities of field-collected populations of 12 mosquito species. After quality filtering and rarefaction, the remaining sequences were assigned to 181 operational taxonomic units (OTUs). Approximately 58% of these OTUs occurred in at least two mosquito species but only three OTUs: Gluconobacter (OTU 1), Propionibacterium (OTU 9), and Staphylococcus (OTU 31) occurred in all 12 mosquito species. Individuals of different mosquito species shared similar gut microbiota and it was common for individuals of the same species from the same study site and collection date to harbor different gut microbiota. On average, the microbiota of Aedes albopictus was the least diverse and significantly less even compared to Anopheles crucians, An. quadrimaculatus, Ae. triseriatus, Ae. vexans, Ae. japonicus, Culex restuans, and Culiseta inornata. The microbial community of Cx. pipiens and Ae. albopictus differed significantly from all other mosquitoes species and was primarily driven by the dominance of Wolbachia.
These findings expand the range of mosquito species whose gut microbiota has been characterized and sets the foundation for further studies to determine the influence of these microbiota on vector susceptibility to pathogens.
The taxonomic characteristics of two bacterial strains, FH5T and SS4, isolated from enrichment cultures obtained from two distinct marine environments, were determined. These bacteria were ...Gram-stain-negative, facultatively anaerobic rods. Growth occurred at 20–40 °C (optimum, 28– 32 °C), pH 5.5–9.0 (optimum, pH 7.0–7.5) and in the presence of 1–7% NaCl (optimum, 2– 4 %). The major cellular fatty acids were anteiso-C(15:0) and iso-C(15:0). Menaquinone 7 (MK-7) was the sole respiratory quinone. The major polar lipids were phosphatidylethanolamine, an unkown phospholipid and an unknown lipid. The DNA G+C contents of strains FH5(T) and SS4 were both determined to be 42.0 mol%. The results of DNA–DNA hybridization studies indicated that the FH5(T) and SS4 genomes share greater than 95% relatedness. The strains formed a distinct phyletic line within the class Bacteroidia, with less than 89.4% sequence similarity to their closest relatives with validly published names. On the basis of physiological and biochemical characteristics, 16S rRNA gene sequences and chemical properties, a novel genus and species, Draconibacterium orientale gen. nov., sp. nov., within the class Bacteroidia, are proposed, with strain FH5T (=DSM 25947(T)=CICC 10585(T)) as the type strain. In addition, a new family, Draconibacteriaceae fam. nov., is proposed to accommodate Draconibacterium gen. nov.
Abstract
Gut microbial communities of mosquitoes can influence vector susceptibility to pathogens, yet the factors that govern their composition remain poorly understood. We investigated the impact ...of host blood-meal source on gut microbiota of Aedes aegypti L. Adult mosquitoes were fed on human, rabbit or chicken blood and their gut microbiota compared to those of sugar-fed and newly emerged adults. Microbial diversity was significantly reduced in blood-fed and sugar-fed mosquitoes but was restored to the levels of newly emerged adults at 7-days post-blood meal. Microbial composition was strongly influenced by host blood-meal source. Leucobacter spp., Chryseobacterium spp., Elizabethkingia spp. and Serratia spp. were characteristic of newly emerged adults and adults fed on chicken, rabbit and human blood, respectively. Sugar-fed mosquitoes had higher abundance of Pseudomonas spp. and unclassified Acetobacteraceae. Shifts in gut microbial communities in response to host blood-meal source may fundamentally impact pathogen transmission given the well-documented link between specific bacterial taxa and vector susceptibility to a variety of mosquito-borne pathogens and may be a key determinant of individual and population variation in vector competence.
Gut bacterial communities of Aedes aegypti shift in response to host blood-meal source.
An isolate of a Gram-positive, facultatively anaerobic, motile, rod-shaped, endospore forming bacterium was recovered from soybean-based fermented paste. It was isolated from cheonggukjang, a Korean ...fermented soybean food product. Phylogenetic analysis of the 16S rRNA gene indicated that the strain was most closely related to Bacillus sonorensis KCTC-13918(T) (99.5 %) and Bacillus licheniformis DSM 13(T) (99.4 %). In phenotypic characterization, the novel strain was found to grow between 15-60 °C and to tolerate up to 10% (w/v) NaCL. Furthermore, the strains grew in media with pH 6 to 11 (optimal growth at pH 7.0–8.0). The predominant cellular fatty acids were anteiso-C(15:0) (37.7%) and iso-C(15:0) (31.5'%). The predominant isoprenoid quinone was menaquinone 7 (MK-7). The cell-wall peptidoglycan contained meso-diaminopimelic acid. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unknown glycolipid. A draft genome of the strain was completed and used for phylogenetic analysis and comparisons to close relatives. The DNA G+C content was 45.9 mol%. In addition, to forming a distinct monophyletic cluster in phylogenetic analysis of gene sequence data, the strain differed from the two most closely related species in that it produces bacitracin, fengycin, a lantipeptide and does not produce lichenicidin. The strains also contained a 9 gene urease cluster and possessed urease activity, not found in closely related species. A phylogenomic analysis of all published genomes of species in the Bacillus licheniformis group revealed that strains belonging to B. licheniformis clustered into two distinct groups, with group 1 consisting of B. licheniformis DSM 13(T) and 11 other strains and group 2 consisting of KJ-16(T) and 4 other strains. This was consistent with other recent B. licheniformis genotyping studies, which showed that it forms at least two distinct groups. Strain KJ-16 and another strain from group 2 were subsequently characterized using a polyphasic taxonomic approach and compared to two strains from group 1 and other type strains of closely related Bacillus species. Based upon the consensus of phylogenetic and phenotypic analyses, we conclude that this strain represents a novel species within the genus Bacillus, for which the name Bacillus paralicheniformis sp. nov. is proposed, with type strain KJ-16(T) (=KACC 18426(T), = NRRL B-65293(T)).
Alternative methods of mosquito control are needed to tackle the rising burden of mosquito-borne diseases while minimizing the use of synthetic insecticides, which are threatened by the rapid ...increase in insecticide resistance in mosquito populations. Fungal biopesticides show great promise as potential alternatives because of their ecofriendly nature and ability to infect mosquitoes on contact. Here we describe the temporospatial interactions between the mosquito Aedes aegypti and several entomopathogenic fungi. Fungal infection assays followed by the molecular assessment of infection-responsive genes revealed an intricate interaction between the mosquito immune system and entomopathogenic fungi. We observed contrasting tissue and time-specific differences in the activation of immune signaling pathways and antimicrobial peptide expression. In addition, these antifungal responses appear to vary according to the fungal entomopathogen used in the infection. Enzyme activity-based assays coupled with gene expression analysis of prophenoloxidase genes revealed a reduction in phenoloxidase (PO) activity in mosquitoes infected with the most virulent fungal strains at 3 and 6d post-fungal infection. Moreover, fungal infection led to an increase in midgut microbiota that appear to be attributed in part to reduced midgut reactive oxygen species (ROS) activity. This indicates that the fungal infection has far reaching effects on other microbes naturally associated with mosquitoes. This study also revealed that despite fungal recognition and immune elicitation by the mosquito, it is unable to successfully eliminate the entomopathogenic fungal infection. Our study provides new insights into this intricate multipartite interaction and contributes to a better understanding of mosquito antifungal immunity.
Fusarium pathogenomics Ma, Li-Jun; Geiser, David M; Proctor, Robert H ...
Annual review of microbiology,
01/2013, Letnik:
67
Journal Article
Recenzirano
Fusarium is a genus of filamentous fungi that contains many agronomically important plant pathogens, mycotoxin producers, and opportunistic human pathogens. Comparative analyses have revealed that ...the Fusarium genome is compartmentalized into regions responsible for primary metabolism and reproduction (core genome), and pathogen virulence, host specialization, and possibly other functions (adaptive genome). Genes involved in virulence and host specialization are located on pathogenicity chromosomes within strains pathogenic to tomato (Fusarium oxysporum f. sp. lycopersici) and pea (Fusarium 'solani' f. sp. pisi). The experimental transfer of pathogenicity chromosomes from F. oxysporum f. sp. lycopersici into a nonpathogen transformed the latter into a tomato pathogen. Thus, horizontal transfer may explain the polyphyletic origins of host specificity within the genus. Additional genome-scale comparative and functional studies are needed to elucidate the evolution and diversity of pathogenicity mechanisms, which may help inform novel disease management strategies against fusarial pathogens.
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