RESUMO
Competition between scavengers and microorganisms for the nutrients within carrion is well documented. As a significant contributor to food web energetics, carrion serves not only as a food source for scavengers, but also as a reproductive resource for many insects. One example are the burying beetles of the Nicrophorus genus (Coleoptera: Silphidae) whose reproduction is dependent on locating and successfully sequestering vertebrate carrion. Throughout the cooperative preparation of carrion and feeding of the larval offspring, parental beetles coat the carrion with oral and anal secretions known to attenuate the growth of molds and bacteria in the laboratory. We test the hypotheses that Nicrophorus secretions attenuate the growth of naturally occurring microorganisms likely to be found colonizing the carrion resource, and that the active antimicrobial components of the secretions are small antimicrobial peptides (AMPs) similar to those produced by other insects.
Assuntos
Peptídeos Catiônicos Antimicrobianos/isolamento & purificação , Secreções Corporais/química , Besouros/fisiologia , Microbiologia do Solo , Animais , Besouros/química , Eletroforese em Gel de Poliacrilamida , Feminino , Masculino , Testes de Sensibilidade Microbiana , Serina ProteasesRESUMO
Cattle are a known reservoir of Shiga toxin-producing Escherichia coli. The prevalence and stability of Shiga toxin and/or Shiga toxin genes among native wild ungulates in Idaho were investigated. The frequency of both Shiga genes and toxin was similar to that reported for Idaho cattle ( approximately 19%).
Assuntos
Animais Selvagens/microbiologia , Proteínas de Escherichia coli/genética , Escherichia coli/genética , Escherichia coli/isolamento & purificação , Toxina Shiga/genética , Fatores de Virulência/genética , Animais , Bovinos , IdahoRESUMO
BACKGROUND: Shiga toxins 1 and 2 (Stx1 and Stx2) are bacteriophage-encoded proteins that have been associated with hemorrhagic colitis, hemolytic uremic syndrome and other severe disease conditions. Stx1 and Stx2 are genetically and immunologically distinct but share the same compound toxin structure, method of entry and enzymatic function. RESULTS: Phylogenetic analysis was performed using Stx1 and Stx2 amino acid and nucleotide sequences from 41 strains of Escherichia coli, along with known stx sequences available from GenBank. The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1. The phylograms showed generally flat topologies among our strains' stx1 and stx2 genes. In the stx2 gene, 39.5% of the amino acid sites display very low nonsynonymous to synonymous substitution ratios. CONCLUSION: The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time. These data could indicate that Shiga toxins are experiencing purifying selection.
Assuntos
Escherichia coli/genética , Toxina Shiga I/genética , Toxina Shiga II/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Bovinos , DNA Bacteriano , Surtos de Doenças , Escherichia coli/classificação , Evolução Molecular , Humanos , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , Toxina Shiga I/química , Toxina Shiga II/químicaRESUMO
We compared PCR amplification of 9 enterohemorrhagic Escherichia coli virulence factors among 40 isolates (21 O/H antigenicity classes) with DNA hybridization. Both methods showed 100% of the chromosomal and phage genes: eae, stx, and stx2. PCR did not detect 4%-20% of hybridizable plasmid genes: hlyA, katP, espP, toxB, open reading frame (ORF) 1, and ORF2.
