Microbial Ecology最新文献

Hydro- and xerohalophytes withstand stress thanks to the resistance traits they have, complemented with the functions of their associated microbiota. Besides, given a higher exposition of the phyllosphere to environmental conditions compared to roots, their endospheric bacteria should be more resistant to stress. In this study, we analysed the composition and functional traits of the bacterial leaf endosphere of six xero- and hydrohalophytes species in two seasons. We sequenced their endospheric metagenomes by shotgun and annotated genes related with Plant-Growth-Promoting (PGP) properties. We showed that the composition, structure and functions of the bacterial endosphere are mainly influenced by host plant species, followed by functional type. Moreover, plant species and functional type promoted a different relative abundance of, respectively, 62 and 6 PGP properties. This study shows that not only the composition but also the functionality of the bacterial leaf endosphere of halophytes is more influenced by host species than functional type. Moreover, the leaf endosphere of the different plant species and functional type could be an important source of bacteria with diverse PGP properties.

Several insect lineages, including some fruit flies, have evolved mutualistic associations with primary symbiotic bacteria. Some species of Tephritinae, the most specialized subfamily of fruit flies (Diptera, Tephritidae) harbour co-evolved, vertically transmitted and non-culturable bacterial symbionts in their midgut, known as Candidatus Stammerula spp. (Enterobacteriaceae). While such associations have previously been reported in the Palearctic and Hawaiian Archipelago, their occurrence in Australasia had not been investigated. In this study we assessed the genetic diversity of eight Australian fruit fly's species from six genera belonging to the Tephritini tribe using mitochondrial markers (16 S rRNA and COI-tRNALeu-COII genes) and compared their bacterial diversity using the 16 S rRNA gene. We detected the presence of specific symbiotic bacteria in all sampled species. Analysis of bacterial 16 S rRNA showed that, with one exception, all Australian symbionts clustered in a well-supported monophyletic clade with Ca. Stammerula detected in Palearctic and Hawaiian Tephritini. Distinct Stammerula lineages were identified in several taxa, while two species, Trupanea prolata and Spathulina acroleuca shared identical symbiont sequences and the same host plant. Notably, Australian and Palearctic Sphenella spp. harboured closely related symbionts. The cophylogenetic analysis revealed a substantial congruence between host and symbiont tree, supporting a history of cospeciation and suggesting biogeographic links between Australasian and Palearctic taxa. Overall, the results expand the geographic knowledge of Tephritini-Ca. Stammerula association and highlight a global pattern of co-diversification.

The subsurface sediments of saline-aquatic systems host diverse microbes, with unclear ecological roles and challenging lab cultivability. Chemolithotrophic anaerobes involved in CO₂-fixation are one of the poorly studied groups. This study focused on understanding these bacteria from subsurface sediments of four representative saline environments, two marine (i.e., Coastal Arabian and Bay of Bengal seas) and two lake (Sambhar and Lonar) systems through enrichment and metagenomics. Enrichment cultures with bicarbonate/CO₂ and hydrogen as the carbon and energy sources, respectively, showed CO₂ fixation, producing acetic and formic acids as the major organic products. Enriched culture with Sambhar Lake sediment produced more formic acid (391 ± 8 mg/L) than acetic acid (92 ± 20 mg/L); however, other enriched cultures produced considerably higher acetic acid (up to 966 ± 24 mg/L) than formic acid (up to 367 ± 30 mg/L). The organics production was accompanied by unique thread-like (up to 500 μm long) aggregates, harbouring chains of rod and oval-shaped microbes in all cultures. Metagenome sequencing revealed dominance of Vibrio spp. (relative sequence abundance of 91% to 97%) across all cultures, while canonical CO₂-fixing taxa were nearly absent (< 0.01%). KEGG analysis revealed partial genes for various CO₂ fixation pathways, including Wood-Ljungdahl, reverse-TCA, dicarboxylate-hydroxybutyrate, hydroxypropionate bicycle, hydroxypropionate-hydroxybutyrate, and the reductive-glycine pathway. The presence of a near-complete serine variant of the reductive glycine pathway, which has been demonstrated in engineered systems, suggests that this pathway may play an operational role in natural systems. The consistent production of organic acids and incomplete pathway representation suggests modular CO₂ fixation within the Vibrio-dominated enriched mixed cultures.

This study uses high-throughput sequencing of the 16S rRNA gene and specific PCR to analyze the microbiome and identify secondary endosymbionts in sand flies from the Amazon region, important vectors of parasitic and viral diseases. Specimens of Psychodopygus, Trichophoromyia, Nyssomyia, Trichopygomyia and Brumptomyia were collected and analyzed. The results revealed that the richness, diversity, and composition of the microbiome are influenced by several factors, such as insect species specific composition, and insect sex. The core microbiome community was represented by 18 genera, with Novosphingobium, Cutibacterium, Methylobacterium and Staphylococcus being the most prevalent. The highest diversity at the genus level was observed in sand flies of epidemiological relevance as Psychodopygus and Nyssomyia, dominated by Novosphingobium (66.5%), Cutibacterium (29.4%) and Methylobacterium (20.4%), while in non-vectors such as Trichophoromyia, Delftia predominated (59.9%). Endosymbiont analysis showed a high prevalence of Cardinium (20%) and Wolbachia (33%), as well as the presence of Spiroplasma, Arsenophonus and Rickettsia. In addition, some bacterial genera related to the inhibition of parasite development, which have entomopathogenic activity and are involved in the degradation of insecticides were identified. Our results are relevant and contribute to the knowledge of the characterization of the microbiome and the endosymbionts in leishmaniasis vectors in the Amazon region and show promise for improving vector management, highlighting the importance of investigating their interaction with pathogens and their impact on vector biology.

Alfalfa (Medicago sativa L.), known as "Queen of forages", is valued to its high-nutritional quality and is a key member of Leguminosae family. Its productivity is largely attributed to mutualistic symbioses with arbuscular mycorrhizal fungi (AMF) and rhizobia, which facilitate nutrient exchange and plant growth. However, the coexistence and mutualistic interactions between rhizobia and AMF across alfalfa genotypes with differing yields in native soil remain poorly understood. In this study, we investigated the community composition of rhizobia and AMF colonizing alfalfa roots across different-yield varieties. Our results showed variations in dominant microbial taxa and the structural complexity of root-associated microbial networks among genotypes. Moreover, rhizobia exhibited no significant associations with AMF on genus level, however, negative correlations were observed among genera within the AMF community, and a comparable trend was identified among rhizobial taxa. In summary, our findings offer new insights into how native soil microbiota influence the dual symbiotic relationships of alfalfa, with implications for leveraging native microbial communities to enhance sustainable forage production.

Insect-microbes holobionts integrate host and microbial functions, with symbionts supporting nutrition, immunity, and defence, while producing metabolites, including beetle-derived compounds with therapeutic potential. Cantharidin is a toxic terpene produced by blister beetles (Coleoptera: Meloidae), endowed with defensive and pharmacological properties. Male insects produce and contain cantharidin in large quantities and transfer it to females upon mating. This study is aimed to gain information about the involvement of insect-associated bacteria in cantharidin biogenesis. To support the possibility that bacteria participate in cantharidin biogenesis, cantharidin antibacterial activity was assessed against six reference strains of representative species of Bacillota and Pseudomonadota from publicly available culture collections. All bacterial strains tolerated concentrations up to 600 µg/ml cantharidin in a standard antibacterial susceptibility test. To identify candidate bacterial lineages, 16S rRNA metataxonomic profiling of the V5-V6 region was performed in males and females from different Meloidae subfamilies and tribes. Analysis of the insect-associated microbiomes of the five cantharidin-producing species (Lydus trimaculatus, Meloe proscarabaeus, Mylabris variabilis, Hycleus polymorphus, Zonitis flava) revealed communities dominated by Pseudomonadota, with secondary contributions from Actinomycetota in Z. flava and M. proscarabaeus and Cyanobacteriota in the other host insects. Although overall community structure and composition did not differ significantly between sexes, a few taxa displayed consistent male-associated patterns, with Staphylococcus, Cutibacterium and one Enterobacteriaceae ASV resulting more abundant in males across all species. The intrinsic bacterial resistance to cantharidin, with both quantitative and qualitative differences in microbiome structure between male and female insects, makes the hypothesis of a putative involvement of bacteria in cantharidin biogenesis still viable.

Recently, there has been a focus on using soil microbes as a means to store carbon in the soil in the form of calcium carbonate, outcomes of which include soil stabilization and biocementation. The molecular processes involved in microbially induced calcium carbonate formation are known, but there is still a significant knowledge gap regarding how community interactions, emergent processes that are distinct from the roles of individual members, may drive the formation of carbonate. To answer these questions, we describe the development and application of a consortium of soil microbes consisting of one species each of the Rhodococcus, Microbacterium, and Curtobacterium genera and two species from the Bacillus genus. We term these five species cultivated together carbon storing consortium A (CSC-A). Growth assays show that only a subset of CSC-A members produces CaCO₃ with Rhodococcus producing the most CaCO₃ but the complete CSC-A produces significantly higher amounts of CaCO₃ compared to the sum total carbonate produced by all member species. The development of CSC-A shows that CaCO₃ production may be as much a community process as it is the contribution of individual species, requiring us to move beyond single species analysis to fully understand carbonate formation by microbial communities in nature. CSC-A will allow the scientific community to ask and answer key questions about the molecular interactions surrounding inorganic carbon formation in soil, an important knowledge gap that must be filled if we wish to stabilize soils and harness microbial processes for materials production.

Wireworms (larvae of different click beetles, Elateridae) are significant soil-borne pest species that can cause severe crop losses. They are difficult to control, and biocontrol using entomopathogenic fungi (EPF) display variable field efficacy. To understand microbial interactions and improve biological control, we studied the interplay between insect and soil microbiota in four wireworm species (Agriotes spp.) at temporal and spatial scales. We found that microbiota associated with wireworms are species-specific and primarily soil-derived. Our results further indicate that ectosymbiotic bacterial community composition on wireworm cuticles is relatively stable over time in specimens not deceasing from spontaneous entomopathogen infection. Therefore, successful microbiome homeostasis on cuticles appears to be correlated with long-term survival of wireworms in soil. Interestingly, EPF were prevalent but low-abundant in all wireworm species as well as in soils. Therefore, we analyzed immune priming effects by low-abundant EPF in soil. Mortality was higher in naïve wireworms than in wireworms pre-exposed to EPFs, and molting frequency increased, indicating both developmental adaptations and immune priming as strategies for EPF avoidance in wireworms. This work disentangles the key components of wireworm microbiomes and highlights the importance of microbial interactions for biocontrol. Biocontrol of wireworms could be improved by considering their species-dependency in microbiome homeostasis as well as physiological and behavioral adaptations to soil-borne pathogens. The potential functional synergies between EPF and soil microbes need further exploration.