Mobile resistome of human gut and pathogen drives anthropogenic bloom of antibiotic resistance.

BACKGROUND: The impact of human activities on the environmental resistome has been documented in many studies, but there remains the controversial question of whether the increased antibiotic resistance observed in anthropogenically impacted environments is just a result of contamination by resistant fecal microbes or is mediated by indigenous environmental organisms. Here, to determine exactly how anthropogenic influences shape the environmental resistome, we resolved the microbiome, resistome, and mobilome of the planktonic microbial communities along a single river, the Han, which spans a gradient of human activities. RESULTS: The bloom of antibiotic resistance genes (ARGs) was evident in the downstream regions and distinct successional dynamics of the river resistome occurred across the spatial continuum. We identified a number of widespread ARG sequences shared between the river, human gut, and pathogenic bacteria. These human-related ARGs were largely associated with mobile genetic elements rather than particular gut taxa and mainly responsible for anthropogenically driven bloom of the downstream river resistome. Furthermore, both sequence- and phenotype-based analyses revealed environmental relatives of clinically important proteobacteria as major carriers of these ARGs. CONCLUSIONS: Our results demonstrate a more nuanced view of the impact of anthropogenic activities on the river resistome: fecal contamination is present and allows the transmission of ARGs to the environmental resistome, but these mobile genes rather than resistant fecal bacteria proliferate in environmental relatives of their original hosts. Video abstract.

Flavobacterium foetidum sp. nov., isolated from ginseng soil.

A Gram-staining-negative bacterial strain, designated CJ42T, was isolated from ginseng soil in Anseong, Republic of Korea. Cells were rod-shaped, yellow-pigmented, aerobic and devoid of flagella but showed gliding motility. Strain CJ42T grew optimally at 30 °C and pH 7.0 in the absence of NaCl on tryptic soy agar. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain CJ42T belonged to the genus Flavobacterium within the family Flavobacteriaceae and was most closely related to Flavobacterium tistrianum KCTC 42679T (97.3 % similarity). Flexirubin-type pigments were produced. The only respiratory quinone was menaquinone 6. The predominant polar lipids were phosphatidylethanolamine, an unknown aminolipid and two unknown lipids. The major fatty acids of strain CJ42T were iso-C15 : 0 and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c). The G+C content of the genomic DNA was 30.7 mol%. Based on the polyphasic analyses, strain CJ42T represents a novel species in the genus Flavobacterium, for which the name Flavobacteriumfoetidum sp. nov. is proposed. The type strain is CJ42T (=KACC 19302=JCM 32085).