Effects of <i>Rhizobium</i> Species Living with the Dark Septate Endophytic Fungus <i>Veronaeopsis simplex</i> on Organic Substrate Utilization by the Host

Abstract

Bacteria harbored in/on the hyphae of the dark septate endophyte, Veronaeopsis simplex Y34, were identified as a single Rhizobium species by molecular analyses of bacterial 16S rRNA genes, and were successfully isolated from the endophyte. The Rhizobium-cured fungus was prepared thoroughly by an antibiotic treatment, thereby allowing an examination of their effects on organic substrate utilization. Assays with Biolog® FF microplates revealed that the respiration potential for 52.6% of the tested compounds were significantly different between Rhizobium-harboring and -cured fungal hosts, indicating that organic substrate utilization by V. simplex Y34 was significantly influenced by the presence of the associated Rhizobium sp. VsBac-Y9.

Density and Diversity of Microbial Symbionts under Organic and Conventional Agricultural Management

“…Community level physiological profiles (CLPP) are most commonly analyzed by the Biolog ® (29) and MicroResp ™ methods (17). The Biolog ® method is a rapid analysis (36, 63), although only a fraction of the microbiome is analyzed due to soil extraction before the reaction. Furthermore, selective carbon sources may change bacterial community structures during the incubation period.…”

Cultivation Renaissance in the Post-Metagenomics Era: Combining the New and Old

“…Fungi-bacteria interactions ( e.g ., Rhizobium sp.-endophytic fungi, soil indigenous bacteria-pathogenic Fusarium sp., and Burkholderiaceae- related endobacteria and plant and soil fungi Mortierella spp.) related to plant growth and health were also investigated (8, 26, 44). Mourad et al .…”

Fungus-Bacterium Symbionts Promote Plant Health and Performance

“…Microbial symbioses are ubiquitous in nature ( 53 ); from protists to humans, all plants and animals are inhabited by microbes that comprise the majority of global biodiversity ( 6 ). In the past two decades, an increasing number of studies have shown that many plant-associated fungi, including foliar ascomycetes ( 1 ), dark septate endophytes (DSEs) ( 18 ), arbuscular mycorrhizal fungi (AMF) ( 4 , 47 ), ectomycorrhizal basidiomycetes ( 3 , 19 ), and sebacinalean endophytes ( 40 ), as well as a few phytopathogenic fungi ( 27 , 31 ) and neutral fungi living in soil ecosystems ( 30 , 37 , 39 , 51 ), harbor phylogenetically diverse bacteria in both epihyphal and endohyphal forms. These bacteria are affiliated to Alpha- , Beta- , Gammaproteobacteria , Mollicutes , Bacillaceae , Chitinophaga , and others, and are known to alter host morphology, sporulation, metabolite production, and even other properties involved in interactions with plants ( 16 , 36 , 41 , 49 ).…”

“…Another noteworthy plant-beneficial fungal group is DSEs, intimately associated with symbiotic bacteria ( 18 ). DSEs are defined as conidial or sterile ascomycetous fungi that colonize the root tissues of diverse plants intracellularly and intercellularly without any harmful effects or typical mycorrhizal structure formation ( 2 , 23 , 29 ).…”

“…Until very recently, the DSE Veronaeopsis simplex Y34 was considered to harbor the bacterial symbiont, Agrobacterium pusense VsBac-Y9, which regulated the carbon metabolism of V. simplex Y34 and enhanced the symbiotic relationship with tomato seedlings ( 17 , 18 ). A series of genes responsible for host interactions with both the fungus and plant were identified in the genome of A. pusense VsBac-Y9, such as the genes involved in the secretion systems of type II and type IV, chitinase, siderophore biosynthesis, cobalamin biosynthesis, and acidic polysaccharide succinoglycan biosynthesis ( 17 ).…”