Mitarai, S. | Search bioRxiv

bioRxiv2018

Six species of non-tuberculosis mycobacteria carry non-identical 16S rRNA gene copies

Non-tuberculosis mycobacteria (NTM) can carry two or more 16S rRNA gene copies that are, in some instances, non-identical. In this study, we used a combined cloning and sequencing approach to analyze the 16S rRNA gene sequences of six NTM species, Mycobacterium cosmeticum, M. pallens, M. hodleri, M. crocinum, M. flavescens, and M. xenopi. The approach facilitated the identification of two distinct gene copies in each species. The two M. cosmeticum genes had a single nucleotide difference, whereas two nucleotide polymorphisms were identified in M. hodleri, M. flavescens, and M. xenopi. M. pallens had a difference in four nucleotides and M. crocinum in 23. Hence, we showed that the six NTM species possess at least two non-identical 16S rRNA gene copies.\n\nImportanceThe presence of multiple 16S rRNA gene copies with nucleotide polymorphisms represents a challenge for species identification using 16S rRNA as the target sequence. Our analysis was focused on six NTM species, M. cosmeticum, M. pallens, M. hodleri, M. crocinum, M. flavescens, and M. xenopi. As a result, we generated the full-length sequences of two non-identical 16S rRNA copies for each NTM species. The data will be helpful for the sequence analysis of specimens or other samples.

bioinformatics↗

bioRxiv2018

Intra-host symbiont diversity and extended symbiont maintenance in photosymbiotic Acantharea (clade F)

Photosymbiotic protists contribute to surface primary production in low-nutrient, open-ocean ecosystems and constitute model systems for studying plastid acquisition via endosymbiosis. Little is known, however, about host-symbiont dynamics in these important relationships, and whether these symbioses constitute mutualisms is debated. In this study, we applied single-cell sequencing methods and advanced fluorescent microscopy to investigate host-symbiont dynamics in clade F acantharians, a major group of photosymbiotic protists in oligotrophic subtropical gyres. We amplified the 18S rRNA gene from single acantharian hosts and environmental samples to assess intra-host symbiont diversity and to determine whether intra-host symbiont community composition directly reflects the available symbiont community in the surrounding environment. Our results demonstrate that clade F acantharians simultaneously host multiple species from the haptophyte genera Phaeocystis and Chrysochromulina. The intra-host symbiont community composition was distinct from the external free-living symbiont community, suggesting that these acantharians maintain symbionts for extended periods of time. After selective staining of digestive organelles, fluorescent confocal microscopy showed that symbionts were not being systematically digested, which is consistent with extended symbiont maintenance within hosts. Extended maintenance within hosts may benefit symbionts through protection from grazing or viral lysis, and therefore dispersal, provided that symbionts retain reproductive capacity.

ecology↗