Changes of Endophytic Bacterial Community in Mature Leaves of Prunus laurocerasus L. during the Seasonal Transition from Winter Dormancy to Vegetative Growth.

Diverse communities of bacterial endophytes inhabit plant tissues, and these bacteria play important roles for plant growth and health. Cherry laurel (Prunus laurocerasus L.) is a broadleaf evergreen shrub that is widely grown in temperate zones for its ornamental and medicinal properties, however virtually nothing is known about its associated bacterial community. In this study, we analysed the matured one-year-old leaves of this plant using Illumina-based 16S rRNA gene metabarcoding to reveal the community structure of endophytic bacteria and understand its shifts during the seasonal transition from winter dormancy to a spring vegetative state. The overall community was composed of four dominant phyla (Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes). Corynebacterium, Acinetobacter, and Chryseobacterium genera were the most prevalent bacteria, comprising 13.3%, 6.9%, and 6.8% of the amplicon sequence variants (ASVs), respectively. The ASV richness and diversity increased significantly in May as compared to other sampling months (February, March, and April). We observed high variation in the overall community structure of endophytic bacteria among collection dates. The variation was only reflected by a few core community members, suggesting that the changes of the endophytic community during winter/spring seasonal transition are mostly associated with the less abundant community members. We identified biomarker taxa for late winter, mid spring, and late spring collection dates. This study is the first one to report on the diversity and composition of bacterial endophytes in the leaves of cherry laurel and its shifts across the dormancy-to-vegetative seasonal transition.

Characterization of Rosa canina Fruits Collected in Urban Areas of Slovakia. Genome Size, iPBS Profiles and Antioxidant and Antimicrobial Activities.

The studies of plant bacterial endophytes, colonizing the plant tissues without any signs of diseases, are essential for understanding of ecological interactions. The aim of our study is to detect microbiological contamination and to assess the antimicrobial, antioxidant activity, total phenolic, carotenoid content, genome size, and ploidy of non-cultivated Rosa canina sampled from urban areas. Samples of Rosa canina fruits were collected in three locations in Slovakia. The highest total viable count and the Enterobacteriaceae count in fruits were 4.32 log CFU/g and 4.29 log CFU/g, respectively. Counts of the mesophilic anaerobic sporulating bacteria, Pseudomonas spp., and of the microscopic fungi and yeasts were 3.00, 2.15 log CFU/g, 3.65 log CFU/g, and 2.76 log CFU/g, respectively. Regarding the antimicrobial activity, Escherichia coli and Klebsiela oxytoca were the most sensitive species among the assayed microorganisms to the treatment with the ethanolic extracts of Rosa canina fruits. The fruits were rich in bioactive compounds, polyphenols, and carotenoids, that could be related to their antioxidant activity. Genome sizes of analyzed samples ranged from 2.3 to 2.96. DNA-based fingerprinting obtained by iPBS markers of the Rosa canina var. lapidicola Heinr. Braun., was characterized by some distinctive inserted loci. An interdisciplinary study was performed for the dog roses from different parts of Slovakia that resulted in deeper characterization of this species.