Spatial structure maintains diversity of pyocin inhibition in household Pseudomonas aeruginosa

Nearly all bacteria produce narrow-spectrum antibiotics called bacteriocins. Studies have shown that bacteriocins can mediate microbial interactions, but the mechanisms underlying patterns of inhibition are less well understood. We assembled a spatially structured collection of isolates of Pseudomonas aeruginosa from bathroom and kitchen sink drains in nine households. Growth inhibition of these P. aeruginosa by bacteriocins, known as pyocins in this species, was measured using pairwise inhibition assays. Carbon source usage of these isolates was measured, and genetic distance was estimated using multilocus sequencing. We found that as the distance between sites of isolation increased, there was a significantly higher probability of inhibition, and that pyocin inhibition and susceptibility vary greatly among isolates collected from different houses. We also detected support for other mechanisms influencing diversity: inhibition outcomes were influenced by the type of drain from which isolates were collected, and while we found no indication that carbon source utilization influences inhibition, inhibition was favoured at an intermediate genetic distance. Overall, these results suggest that the combined effects of dispersal limitation among sites and competitive exclusion within them maintain diversity in pyocin inhibition and susceptibility phenotypes, and that additional processes such as local adaptation and effects of phylogenetic distance could further contribute to spatial variability.

Molecular identification of Trichogramma species from South and South-East Asia and natural Wolbachia infection

Trichogramma wasps were collected from the parasitized eggs of lepidopteran pests from 21 sampling sites in East Asia and South-East Asia. Six Trichogramma species were identified based on the molecular identificationmethod using the internal transcribed spacer 2 (ITS2) region of the rDNAof Trichogramma chilonis, T. evanescens, T. ostriniae, T. embryophagum, T. dendrolimi and T. japonicum. The results of molecular identification were confirmed by morphological identification. Additionally, natural populations were screened for the prevalence of Wolbachia. Five out of 21 populations were infected by the same Wolbachia strain, which was identified by using Wolbachia wsp gene and multilocus sequencing approach. The phylogenetic analysis of Wolbachia wsp sequences revealed that the Wolbachia strain was classified in the strain wEvaA in the group of EvA of the supergroup A.

Listeriosis: genotyping as a key for identification a possible source of infection

Objective. To perform a comparative analysis of clinical and food isolates of Listeria monocytogenes collected in the European part of Russia in 2018–2019. Materials and Methods. We used multilocus sequencing (MLST), supplemented by virulence loci, including fragments of internalin genes (MvLST, Multi-virulent-locus sequence typing), followed by phylogenetic analysis. Results. The main diagnoses for clinical isolates were prenatal and neonatal listeriosis and meningitis. Clinical isolates predominantly belonged to phylogenetic line II with the predominance of ST7, which was also the most abundant in food isolates. The second most common occurrence in food isolates was ST121, widely distributed in Europe. Isolates of phylogenetic line I in the group of clinical cultures in three cases were represented by ST6, detected during outbreaks of listeriosis in Europe 2015–2018 and South Africa in 2017–2018. Only in one isolate from food belonged to the phylogenetic lineage I. In general, the diversity of food isolate genotypes was significantly higher than clinical isolates. The analysis of virulence loci revealed a new internalin A allele and a new internalin genes profile (IP) in isolate ST7 from food. Conclusions. L. monocytogenes of the most common ST7 is autochthonous in Russia; cases of listeriosis caused by the ST6 bacterium are most likely imported. Based on the analysis of the diversity of ST and IP of L. monocytogenes identified in Russia, a rapid diagnosis scheme for epidemiological investigation is proposed.

Multilocus sequencing-based evolutionary analysis of 52 strains of Burkholderia pseudomallei in Hainan, China

Previously, we reported a phylogenetic study of 98 Burkholderia pseudomallei clinical isolates from Hainan, China. Here, we update the B. pseudomallei strain library with 52 strains from newly identified cases dating from 2014 to 2017, analysed by multilocus sequence typing. Twenty-two sequence types (STs) were identified from the 52 cases, illustrating high genetic diversity; five of them (ST1480, ST1481, ST1482, ST1483 and ST1484) were novel. ST46, ST50 and ST58 predominated (34.6%) as was the case in the previous study (35.7%). An e-BURST map of the ST profiles of the two collections of isolates showed their genetic foundation to be largely unchanged. Neighbour-joining tree analysis was suggestive of a close phylogenetic relationship between the novel STs from this series and those first reported from Hainan (ST1105, ST1099, ST55 and ST1095). Moreover, the two novel STs (1481 and 1483) showed close similarity to ST58 which originated in Thailand indicating a close relationship between B. pseudomallei strains from both countries. The previously described allele profiles gmhD-36 and lepA-68 were found for the first time in our strain collections. Our study emphasises the importance of monitoring the epidemiological status and evolutionary trends of B. pseudomallei in China.

Characterisation of the dimorphic Deladenus beddingi n. sp. and its associated woodwasp and fungus

Summary A new dimorphic species of Deladenus isolated from Sirex californicus from Washington, USA, is described as D. beddingi n. sp. Evolutionary relationships of the new species with other Deladenus species were assessed using multilocus sequencing. Phylogenetic relationships derived from analyses of mtCO1 and ITS showed D. beddingi n. sp. to be genetically distinct from other North American Deladenus parasitising Sirex. Molecular analyses indicated that D. beddingi n. sp. is a member of the D. siricidicola species complex, which also includes undescribed native Deladenus from Sirex cyaneus and S. nitidus, and D. siricidicola from S. noctilio. Mycophagous adults were characterised by the position of the excretory pore, which was located 32 (22-52) and 48 (38-69) μm anterior to the hemizonid in mycophagous females and males, respectively. Typologically, the new species is most similar to D. siricidicola, D. proximus and D. nitobei, but can be distinguished from these species by several morphometric traits, including the value of ratios a, b, c of the mycophagous females and males, ratio b of the infective females, and the morphology of the tail of the mycophagous females, which is narrow and gradually tapering. This novel nematode species feeds on the fungus Amylostereum chailletii during its mycophagous phase. Experimental results showed very little reproduction by D. beddingi n. sp. when feeding on A. areolatum compared to robust reproduction when feeding on A. chailletii.