Leaf-associated microbiota on perilla (Perilla frutescens var. frutescens) cultivated in South Korea to detect the potential risk of food poisoning.

Perilla (Perilla frutescens) is a commonly consumed herb with various health benefits in Asia. However, the risks of food-borne illness owing to the presence of pathogens on perilla leaves have not been evaluated. In this study, we evaluated the microbiota of perilla leaves harvested in South Korea using Illumina MiSeq sequencing of the 16S rRNA gene. In total, 2,743,003 sequencing reads were obtained, and 92-437 operational taxonomic units were observed in all samples. Bacterial loads were quantified, and the diversity indices were compared. Differences in the microbiota among sampling times and regions were also investigated. Proteobacteria and Firmicutes were predominant phyla at both times. At the class level, the bacterial communities were composed primarily of Alphaproteobacteria, Bacilli, and Gammaproteobacteria. Diverse bacterial taxa, such as Bacillus, uncultured family Enterobacteriaceae, and Sphingomonas were detected, and the representative pathogenic species (i.e., Acinetobacter lwoffii, Klebsiella pneumoniae, and Staphylococcus aureus) were quantified by qRT-PCR. The results of the co-occurrence network analysis showed characteristics of bacterial taxa in the microbiome on perilla leaves and provided insights into the roles of correlations among diverse microbes, including potential pathogens. Based on these results, the potential risk of food-borne illness from consumption of perilla leaves may be higher in July than in April. In summary, the microbial compositions determined in this study can be used as a base data for food-safety management for prediction and prevention of future outbreaks.

Colletotrichum shisoi sp. nov., an anthracnose pathogen of Perilla frutescens in Japan: molecular phylogenetic, morphological and genomic evidence.

Species of the fungal genus Colletotrichum are among the most devastating pathogens of agricultural crops in the world. Based on DNA sequence data (ITS, GAPDH, CHS-1, ACT, TUB2) and morphology, we revealed Colletotrichum isolates infecting the oil crop Perilla frutescens, commonly known as shiso, to represent a previously unknown species of the C. destructivum species complex and described it as C. shisoi. We found that C. shisoi appears to be able to adopt a hemibiotrophic lifestyle, characterised by the formation of biotrophic hyphae followed by severe necrotic lesions on P. frutescens, but is less virulent on Arabidopsis, compared to its close relative C. higginsianum which also belongs to the C. destructivum species complex. The genome of C. shisoi was sequenced, annotated and its predicted proteome compared with four other Colletotrichum species. The predicted proteomes of C. shisoi and C. higginsianum, share many candidate effectors, which are small, secreted proteins that may contribute to infection. Interestingly, C. destructivum species complex-specific secreted proteins showed evidence of increased diversifying selection which may be related to their host specificities.

Nocardioides perillae sp. nov., isolated from surface-sterilized roots of Perilla frutescens.

A Gram-stain-positive, rod-shaped actinobacterium, designated strain I10A-01402(T), was isolated from surface-sterilized roots of a medicinal plant, Perilla frutescens, collected in a suburb of Beijing, China. Chemotaxonomically, the strain contained ll-diaminopimelic acid as the diagnostic diamino acid and MK-8(H4) as the predominant menaquinone. The phospholipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol. The major fatty acids were C17 : 1ω9c, C18 : 1ω9c, C17 : 0, C16 : 0 and iso-C16 : 0. The genomic DNA G+C content was 70.4 mol%. 16S rRNA gene sequence analysis indicated that strain I10A-01402(T) belonged to the genus Nocardioides. Phylogenetic analyses based on 16S rRNA gene sequences showed that the isolate formed a robust cluster with Nocardioides ginsengisegetis Gsoil 485(T), N. koreensis MSL-09(T) and N. alkalitolerans KSL-1(T). On the basis of the evidence from our polyphasic taxonomic study, a novel species, Nocardioides perillae sp. nov., is proposed. The type strain is I10A-01402(T) ( = CPCC 203382(T)  = DSM 24552(T)  = KCTC 29022(T)).

Paenibacillus elgii sp. nov., with broad antimicrobial activity.

Two novel spore-forming bacteria with broad antimicrobial activity were isolated from roots of Perilla frutescens. The isolates, SD17(T) and SD18, were facultatively anaerobic and showed variable Gram reaction. Growth was observed between 20 and 45 degrees C. DNA G+C content of SD17(T) was 51.7 mol%, and the major fatty acid was anteiso-C(15 : 0) (54.1 %). 16S rRNA gene sequence similarity of SD17(T) ranged from 98.6 to 91.3 % with other Paenibacillus species. The phylogenetic tree showed that isolate SD17(T) formed a significant monophyletic clade with Paenibacillus koreensis KCTC 2393(T) and Paenibacillus ehimensis IFO 15659(T). DNA-DNA relatedness values for strain SD17(T) with Paenibacillus koreensis KCTC 2393(T) and Paenibacillus ehimensis IFO 15659(T) were 17.4 and 19.8 %, respectively. These isolates thus merit species status within Paenibacillus, for which the name Paenibacillus elgii sp. nov. is proposed. The type strain is SD17(T) (=KCTC 10016BP(T)=NBRC 100335(T)).