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Absence of genome reduction in diverse, facultative endohyphal bacteria

Journal Article · · Microbial Genomics

Fungi interact closely with bacteria, both on the surfaces of the hyphae and within their living tissues (i.e. endohyphal bacteria, EHB). These EHB can be obligate or facultative symbionts and can mediate diverse phenotypic traits in their hosts. Although EHB have been observed in many lineages of fungi, it remains unclear how widespread and general these associations are, and whether there are unifying ecological and genomic features can be found across EHB strains as a whole. We cultured 11 bacterial strains after they emerged from the hyphae of diverse Ascomycota that were isolated as foliar endophytes of cupressaceous trees, and generated nearly complete genome sequences for all. Unlike the genomes of largely obligate EHB, the genomes of these facultative EHB resembled those of closely related strains isolated from environmental sources. Although all analysed genomes encoded structures that could be used to interact with eukaryotic hosts, pathways previously implicated in maintenance and establishment of EHB symbiosis were not universally present across all strains. Independent isolation of two nearly identical pairs of strains from different classes of fungi, coupled with recent experimental evidence, suggests horizontal transfer of EHB across endophytic hosts. Given the potential for EHB to influence fungal phenotypes, these genomes could shed light on the mechanisms of plant growth promotion or stress mitigation by fungal endophytes during the symbiotic phase, as well as degradation of plant material during the saprotrophic phase. As such, these findings contribute to the illumination of a new dimension of functional biodiversity in fungi.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1379745
Journal Information:
Microbial Genomics, Journal Name: Microbial Genomics Journal Issue: 2 Vol. 3; ISSN 2057-5858
Publisher:
Society for General MicrobiologyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (6)

An Endohyphal Bacterium (Chitinophaga, Bacteroidetes) Alters Carbon Source Use by Fusarium keratoplasticum (F. solani Species Complex, Nectriaceae) journal March 2017
Managing plant-environment-symbiont interactions to promote plant performance under low temperature stress journal August 2019
Mixta gen. nov., a new genus in the Erwiniaceae journal April 2018
The fungal holobiont: Evidence from early diverging fungi journal April 2017
Unveiling Concealed Functions of Endosymbiotic Bacteria Harbored in the Ascomycete Stachylidium bicolor journal June 2018
Complete Genome Sequence of Luteibacter pinisoli MAH-14 journal July 2019


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