The aim of this study was to determine the presence of the hyperparasitic fungus Arthrorhynchus nycteribiae and to analyze its spatio-temporal pattern in the two bat flies (Penicillidia conspicua and P. dufourii) parasitizing on bats. We collected 612 samples of bat flies from 400 bats in 20 caves in the Central Balkans. Hyperparasite was identified based on morphological and molecular analyses of rDNA genes (LSU and SSU). A. nycteribiae was reported for the first time in Bosnia and Herzegovina and Montenegro, and confirmed in Serbia. Of the 20 sites examined, we found A. nycteribiae at 11 sites. The prevalence of A. nycteribiae infection in the bats examined was approximately 17%. Miniopterus schreibersii harbored the highest number of bat flies and was the only bat species hosting the infected bat flies of the species P. conspicua. Our results showed significant differences in infection patterns during the different seasons: the highest prevalence of bat flies with hyperparasitic fungi was found in the summer season (23%) and the lowest in spring (2%). Female bat fly hosts showed a significantly higher prevalence of infection than male bat flies. This study makes an important contribution to the knowledge of the distribution of A. nycteribiae and to the understanding of complex parasite-host relationships in the poorly studied areas of the Central Balkans.

Prasiola is a genus of foliose green algae that forms extensive cryptogamic canopies that contribute to the greening of ice-free areas in the Antarctic tundra. To better understand the impact of Prasiola canopy establishment on colonization in these areas, this study compared the taxonomic and functional structures of bacterial and fungal communities in adjacent soils with and without extensive Prasiola colonization. DNA metabarcoding was employed to analyze the microbial community structure in these soils and in the canopy. Additionally, a phylogenetic study of Prasiola samples was conducted to characterize the taxonomic composition of the analyzed canopies, revealing the presence of Prasiola crispa (Lightfoot) Kützing and P. antarctica Kützing. Key soil attributes were assessed to examine the canopy’s influence. Higher pH and carbon, nitrogen, and organic matter contents were found in Prasiola-covered soils than in bare soils. Furthermore, Prasiola canopy establishment not only influenced abiotic soil properties but also shaped soil microbial community structure and its functions. For instance, while Actinobacteriota predominated in bacterial communities both within the Prasiola canopy and beneath it, Bacteroidota dominated in the bare soil. Despite significant variability across soil types, fungal communities showed a trend of higher abundances in certain Ascomycetes, such as Helotiales, Hypocreales, or Xylariales, in soils beneath Prasiola compared to bare soils. Regarding functional diversity, covered soils exhibited a statistically significant lower potential for bacterial methanogenesis and autotrophic CO2 fixation compared to bare soils. Finally, lichenized fungi, plant pathogens, and fungal wood saprotrophs tended to be more abundant in covered soils.

Grasslands are important centers of biodiversity; however, these ecosystems have been in decline. Although many methods for grassland restoration have been developed, the abundant microbial communities in these regions are understudied and could be used to assist in these efforts. In this study, we aimed to understand how microbial communities varied by soil type, grassland site, and environmental conditions. Samples were taken from rhizosphere soil (attached to plant roots), proximal soil (close to the plant roots), and from bulk cores at Ricketts Glen State Park and Nescopeck State Park in northeastern Pennsylvania, USA, during June and August of 2021 and 2022. Rhizosphere soil samples were taken from the native common grassland plant, Solidago rugosa. 16S rRNA gene sequencing revealed that pH as well as soil type (bulk, proximal, or rhizosphere) significantly influenced the microbial community composition of each soil. Each soil type had its own distinct microbial communities, and proximal soil was identified as a transition zone between rhizosphere and bulk microbial communities. We also observed that the rhizosphere communities were dependent upon geography, as these communities were significantly different between grasslands even though the plant species remained the same. Our results highlight the complex nature of soil microbial communities and how many factors, including pH, soil type, and geography, can be overlayed to impact soil microbes. Results suggest future avenues of conservation research through modification and regulation of specific soil microbial communities in order to aid in the rehabilitation of these diminished regions.

The formation of biofilms in industrial environments poses a significant challenge because of their ability to degrade materials, contaminate products, and harbour pathogenic microorganisms. In the automotive industry, surface treatment systems (STS) used to prepare car bodies can provide a favourable environment for microbial development, driven by the presence of water, organic matter, and variable physicochemical conditions. In this context, the microbial diversity present in the different STS baths of an automotive plant, as well as in the process water, was analysed. Through culture-based methods and molecular analysis, 33 bacterial and 6 yeast species were identified. The results revealed a constant presence of bacteria at all sampling points, whereas yeasts were detected less frequently and in more localized areas (Industrial and Dechromatized Water, E2, Conversion stage, E4 and Passivation stage). This study underscores the importance to enhance cleaning and disinfection protocols in STS, as high bacterial counts persisted even after rinsing stages, in order to prevent economic losses, product degradation and health risks. Furthermore, it highlights the potential use of certain microorganisms in biotechnology and bioremediation applications.

Marine sponges are widespread, sessile, filter-feeding animals, known for living in association with complex prokaryotic communities structured by host species. Though marine fungi are ubiquitous across marine environments, little is known about sponge-associated fungal communities (mycobiome). Indeed, aside from a few studies based on the isolation of fungal strains for biotechnological purposes, little information is available to understand the diversity and structure of sponge mycobiome. Here, a metabarcoding approach based on the ITS1 marker was applied to examine the structure and composition of fungal communities associated with four Mediterranean sponges. The species: Petrosia ficiformis, Chondrosia reniformis, Crambe crambe, and Chondrilla nucula were analyzed along with the surrounding seawater, revealing Aspergillus (1–56%), Cladosporium (1–75%), Malassezia (1–38.5%), and Pennicillium (1.5–36%) as the most represented fungal genera. Our data showed high intra-specific variability and no clear core mycobiome within each of the sponge species host, suggesting stochastic and perhaps transient community membership. This study sheds light on one of the most abundant yet least understood components of the marine ecosystem. Unraveling the dynamics of fungal interactions within sponge holobionts is essential to advance our understanding of their ecological roles and functions. By addressing the enigmatic nature of sponge-associated fungi, this research opens new avenues for exploring their contributions to marine ecosystems and resolving the many unanswered questions in this field.

Geosmin is a volatile organic compound (VOC) produced by a range of different soil microorganisms, and is most commonly recognized for its characteristic “earthy” scent evident after rainfall. Though it remains unclear why microorganisms produce geosmin, we know that exposure to geosmin can influence behaviors across a wide range of organisms, serving as both an attractant and a repellant, but geosmin effects on soil protists remain largely unstudied. We investigated how soil protists respond to geosmin exposures, focusing on representatives of three morphological groups of protists, Colpoda sp. (ciliate), Cercomonas sp. (flagellate), and Acanthamoeba castellanii (naked amoeba), testing the hypothesis that geosmin production by bacteria influences soil protist behavior. We conducted experiments to evaluate protist excystment (waking up) and predation responses to geosmin-producing (Streptomyces coelicolor M145) and non-producing (S. coelicolor J3003) bacteria, as well as synthetic geosmin. All three protists excysted at higher rates when exposed to geosmin-producing bacteria or synthetic geosmin, while no significant excystment occurred with the non-producing strains or in the absence of synthetic geosmin. Protist feeding preferences were also affected, with two of the three protists (Cercomonas sp. and A. castellanii) less likely to predate geosmin-producing versus non-producing bacterial strains. Our findings suggest that soil protists can detect geosmin as a signal indicating favorable soil conditions and geosmin production by bacteria may serve as a deterrent to predation by protists. More generally, our results highlight the ecological significance of geosmin in the soil food web and its role in mediating bacteria-protist interactions.

Henan province is a major peanut-producing area in China, but research on rhizobia nodulating peanut have been limited to southern Henan, which accounts for only less than half of the province. A collection of 212 strains of peanut rhizobia was obtained from six field sites in eastern, central, and northern Henan, Central China, by using peanut as a trap host under glasshouse conditions. PCR–RFLP analysis of ribosomal IGS sequences classified the 212 strains into 28 distinct types. Phylogenetic analyses of the 16S rRNA, atpD, gyrB, dnaK, and rpoB genes from 30 representative strains of the 28 IGS types identified revealed the presence of Bradyrhizobium. liaoningense, B. yuanmingense, B. zhengyangense, and two novel Bradyrhizobium genospecies. This composition differs from the peanut rhizobia community found in southern Henan. B. liaoningense was the dominant species, covering 49% of the total isolates across the field sites, while B. zhengyangense accounting for 27%, B. yuanmingense for 7% and the two novel Bradyrhizobium genospecies for 17%. Phylogenetic analysis showed that the symbiosis-related nodC and nifH gene sequences clustered into six groups: three associated exclusively with the peanut host (symbiovar arachidis and two unnamed group), three originating from other legume hosts (sv. glycinearum, cajani and retamae). Through the principal component analysis (PCA) between IGS types or species and soil physicochemical properties and environmental factors, it showed that IGS types 1, 3, 5, 8, 9, 12, 14, 15, 18, and 21 positively correlated with AveTmax, AveTmin, AN and AP. IGS types 4, 11, 16, 17, 20, 25, and 26 were positively associated with Alt, AvePrecp, and pH. IGS types 2, 7, 10, 22, 24, and 27 correlated with AP, while remaining types exhibited correlations with OM. In addition, B. yuanmingense, B. liaoningense, and Bradyrhizobium genosp. I positively affected by AveTmax, AP, AN, and AK. Bradyrhizobium genosp. II positively correlated with AK, AN, and OM while B. zhengyangense mainly affected by AvePrecp and pH. The alkaline soil pH in this study differs greatly from the acid soils in southern Henan, explaining the inconsistency between the species of peanut rhizobia detected in southern Henan and the rest of the province. The symbiotic effect assay demonstrated that all representative strains successfully formed nodules and exhibited a significant increase in symbiotic efficiency. Representative strains revealed diverse abiotic stress tolerance to NaCl, acidity, alkalinity, temperature and drought. It conducted a comprehensive collection of peanut rhizobia in eastern, central, and northern Henan province, identifying two putative novel Bradyrhizobium species and isolating rhizobial strains with high symbiotic efficiency and robust stress tolerance. This study is a necessary basic for the producing and application of peanut rhizobial inoculant in this main agricultural province.

This study aimed to investigate the presence and abundance of antibiotic resistance genes (ARGs) in bacterial and phage DNA fractions from sediment samples collected from the Onyar River, both before and after its passage through the urban area of Girona (northeast Spain). Genes conferring resistance to β-lactams, fluoroquinolones, macrolides, sulfonamides, and tetracyclines were quantified using quantitative PCR. Our findings showed that ARGs are present in both bacterial and phage DNA fractions, with a higher abundance in the bacterial fraction. Notably, our analysis revealed an increased abundance of the sulfonamide resistance gene sulI in the phage DNA fraction when comparing samples collected before and after the river’s passage through the city. Although similar trends were observed for other ARGs (e.g., qnrS and sulII), these differences were not statistically significant (p > 0.05). These findings emphasize the importance of phages as potential reservoirs or vehicles for ARGs in environmental settings. Further research is needed to elucidate the factors that influence gene transfer dynamics and the persistence of ARGs within phages.

The order Holosporales is a broad and ancient lineage of bacteria obligatorily associated with eukaryotic hosts, mostly protists. Significantly, this is similar to other evolutionary distinct bacterial lineages (e.g. Rickettsiales and Chlamydiae). Here, we provide a detailed and comprehensive account on the current knowledge on the Holosporales. First, acknowledging the up-to-date phylogenetic reconstructions and recent nomenclatural proposals, we reevaluate their taxonomy, thus re-ranking them as a suborder, i.e. Holosporineae, within the order Rhodospirillales. Then, we examine the phylogenetic diversity of the Holosporineae, presenting the 20 described genera and many yet undescribed sub-lineages, as well as the variety of the respective environments of provenance and hosts, which belong to several different eukaryotic supergroups. Noteworthy representatives of the Holosporineae are the infectious intranuclear Holospora, the host manipulator ‘Caedimonas’, and the farmed shrimp pathogen ‘Candidatus Hepatobacter’. Next, we put these bacteria in the broad context of the whole Holosporineae, by comparing with the available data on the least studied representatives, including genome sequences. Accordingly, we reason on the most probable evolutionary trajectories for host interactions, host specificity, and emergence of potential pathogens in aquaculture and possibly humans, as well as on future research directions to investigate those many open points on the Holosporineae.

Poly(butylene succinate-co-adipate) (PBSA), a biodegradable plastic, is significantly colonized and degraded by soil microbes under natural field conditions, especially by fungal plant pathogens, raising concerns about potential economic losses. This study hypothesizes that the degradation of biodegradable plastics may increase the presence and abundance of plant pathogens by serving as an additional carbon source, ultimately posing a risk to forest ecosystems. We investigated (i) fungal plant pathogens during the exposure of PBSA in European broadleaved and coniferous forests (two forest types), with a specific focus on potential risk to tree health, and (ii) the response of such fungi to environmental factors, including tree species, soil pH, nutrient availability, moisture content, and the physicochemical properties of leaf litter layer. Next-generation sequencing (NGS) revealed that PBSA harbored a total of 318 fungal plant pathogenic amplicon sequence variants (ASVs) belonging to 108 genera. Among the identified genera (Alternaria, Nectria, Phoma, Lophodermium, and Phacidium), some species have been reported as causative agents of tree diseases. Plenodomus was present in high relative abundances on PBSA, which have not previously been associated with disease in broadleaved and coniferous forests. Furthermore, the highest number of fungal plant pathogens were detected at 200 days of PBSA exposure (112 and 99 fungal plant pathogenic ASV on PBSA degraded under Q. robur and F. sylvatic-dominated forest, respectively), which was double compared mature leaves and needles from the same forest sites. These findings suggest that PBSA attracts fungal plant pathogens in forests as an additional carbon source, potentially leading to increased disease outbreaks and disrupting the stability of forest ecosystems. The fungal plant pathogenic community compositions were mainly shaped by forest type, PBSA exposure time, site locations, leaf litter layer water content, and N:P ratio from leaf litter layer in both forest types. This study provides valuable insights into the potential risks posed by biodegradable plastic degradation in forests after 200 and 400 days of exposure, respectively. Further comprehensive evaluations of their effects on tree health and ecosystems, ideally on a long-term basis, are needed. These evaluations should include integrating microbial investigation, soil health monitoring, and ecosystem interaction assessments. Nevertheless, it should be noted that our interpretation of plant pathogens is solely based on high-throughput sequencing, bioinformatics, and annotation tools.