Trichothecium roseum is one of the most important postharvest pathogens in arid and semiarid regions. Sodium silicate (NaSi) and environmental pH have significant inhibitory effects on fungal growth. ...However, no study has addressed the relationship of NaSi and pH in combination and the effects on T.roseum. In this work, we showed that spore germination, germ tube elongation, and mycelial growth of T.roseum were significantly inhibited by various NaSi concentrations, which had corresponding increasing pHs. Furthermore, these NaSi solutions showed a much greater impact than did pH treatments alone. The pathogenicity of NaSi-treated conidia on a model assay (conidia-inoculated apple fruit) was dramatically reduced, whereas no changes of pathogenicity were evident for the corresponding pH (various sodium hydroxide (NaOH) solutions) treatments. Fluorescent microscopy, using propidium iodide staining, showed damage of the plasma membranes of T.roseum conidia treated with both NaSi and NaOH, although the damage was more severe with NaSi. Leakage of proteins and sugars was significantly higher in NaSi-treated and NaOH-treated conidia than in untreated controls. In addition, serious damage was observed in the conidia exposed to NaSi for longer periods of time. Ultrastructural observations showed that treatment with either NaSi or NaOH caused a plasmolysis state and disorganized organelles. Taken together the results show that NaSi has inhibitory effects on T.roseum and that the inherent higher pH of NaSi solutions of higher concentrations simply acts as an enhancer of the inhibitory effects of NaSi.
Centella asiatica
(L.) Urban is a highly considered medicinal plant owing to its secondary metabolites asiaticoside, madecassoside, asiatic acid, and madecassic acid. The asiaticoside, one of the ...most important constituents of the plant, is a triterpenoid saponin having memory enhancement property. Given its medicinal properties, we isolated and characterized endophytic fungi from this plant with the aim to screen these microorganisms for asiaticoside production. In total, we isolated 13 endophytic fungi from the leaves of the plant, out of which one of the isolates produced asiaticoside. This asiaticoside producing isolate was identified as
Colletotrichum gloeosporioides
by internal transcribed spacer-based rDNA sequencing. The presence of asiaticoside in ethyl acetate extract of
C. gloeosporioides
was confirmed by LC–MS. The production of asiaticoside measured in relation to incubation time and subculture generation revealed presence of 62.29 ± 3.36 µg/100 mL of asiaticoside by
C. gloeosporioides
on the 15th day in first subculture generation followed by a decrease in subsequent generations. A similar trend was also shown by yield and growth curve of
C. gloeosporioides
. The asiaticoside production and yield were found to be positively correlated. This paper reported the production of asiaticoside by an endophytic fungus
C. gloeosporioides
for the first time. The present findings definitely provide an impetus to the production of asiaticoside by utilizing the endophytic source.
Graphical Abstract
Chemical compound studied in this article: Asiaticoside (PubChemCID: 108062)
N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this ...greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order-particularly Fusarium oxysporum and Trichoderma spp.-and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O (15)N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment.
Autoluminescent plants engineered to express a bacterial bioluminescence gene cluster in plastids have not been widely adopted because of low light output. We engineered tobacco plants with a fungal ...bioluminescence system that converts caffeic acid (present in all plants) into luciferin and report self-sustained luminescence that is visible to the naked eye. Our findings could underpin development of a suite of imaging tools for plants.
The indoor microbiome is a complex system that is thought to depend on dispersal from the outdoor biome and the occupants' microbiome combined with selective pressures imposed by the occupants' ...behaviors and the building itself. We set out to determine the pattern of fungal diversity and composition in indoor air on a local scale and to identify processes behind that pattern. We surveyed airborne fungal assemblages within 1-month time periods at two seasons, with high replication, indoors and outdoors, within and across standardized residences at a university housing facility. Fungal assemblages indoors were diverse and strongly determined by dispersal from outdoors, and no fungal taxa were found as indicators of indoor air. There was a seasonal effect on the fungi found in both indoor and outdoor air, and quantitatively more fungal biomass was detected outdoors than indoors. A strong signal of isolation by distance existed in both outdoor and indoor airborne fungal assemblages, despite the small geographic scale in which this study was undertaken (<500 m). Moreover, room and occupant behavior had no detectable effect on the fungi found in indoor air. These results show that at the local level, outdoor air fungi dominate the patterning of indoor air. More broadly, they provide additional support for the growing evidence that dispersal limitation, even on small geographic scales, is a key process in structuring the often-observed distance-decay biogeographic pattern in microbial communities.
Most plants form symbiotic associations with arbuscular mycorrhizal fungi (AMF). AMF increase the uptake of plant nutrients by extending their extra-radical mycelium (ERM) in the soil where other ...groups of microorganisms may suppress the activity of the ERM. However, little is known about such suppression in natural soils. This work aimed to investigate the incidence of AMF suppression among soils sampled from highly variable natural ecosystems, and used 33P uptake by the ERM to evaluate AMF activity. A second aim was to identify factors behind the observed AMF-suppression. We found that AMF-suppressiveness varied markedly among natural soils and occurred more frequently in low pH than in high pH soils. A previous study for cultivated soils revealed a strong biological component of suppressiveness against AMF, and in accordance we found that the composition of both fungal and bacterial communities differed significantly between AMF-suppressive and non-suppressive natural soils. Acidobacteria, Acidothermus, Xanthomonadaceae, Archaeorhizomyces sp., Mortierella humilis and some Mycena spp. were significantly more abundant in AMF-suppressive soils and may therefore be direct antagonists of AMF. This implies that the functioning of AMF in natural ecosystems is strongly modulated by specific soil microbes.
Bacterial and fungal co-infection has been reported in patients with COVID-19, but there is limited experience on these infections in critically ill patients. The objective of this study was to ...assess the characteristics and ouctome of ICU-acquired infections in COVID-19 patients. We conducted a retrospective single-centre, case-control study including 140 patients with severe COVID-19 admitted to the ICU between March and May 2020. We evaluated the epidemiological, clinical, and microbiological features, and outcome of ICU-acquired infections. Fifty-seven patients (40.7%) developed a bacterial or fungal nosocomial infection during ICU stay. Infection occurred after a median of 9 days (IQR 5–11) of admission and was significantly associated with the APACHE II score (
p
= 0.02). There were 91 episodes of infection: primary (31%) and catheter-related (25%) bloodstream infections were the most frequent, followed by pneumonia (23%), tracheobronchitis (10%), and urinary tract infection (8%) that were produced by a wide spectrum of Gram-positive (55%) and Gram-negative bacteria (30%) as well as fungi (15%). In 60% of cases, infection was associated with septic shock and a significant increase in SOFA score. Overall ICU mortality was 36% (51/140). Infection was significantly associated with death (OR 2.7, 95% CI 1.2–5.9,
p
= 0.015) and a longer ICU stay (
p
< 0.001). Bacterial and fungal nosocomial infection is a common complication of ICU admission in patients with COVID-19. It usually presents as a severe form of infection, and it is associated with a high mortality and longer course of ICU stay.
Summary
Microbes play an important role in decomposition of macrophytes in shallow lakes, and the process can be greatly affected by bacteria–fungi interactions in response to material composition ...and environmental conditions. In this study, microbes involved in the decomposition of leaf litter from three macrophyte species, Zizania latifolia, Hydrilla verticillata and Nymphoides peltata, were analysed at temperatures of 5, 15 and 25 °C. Results indicate that the decomposition rate was affected by temperature. Bacterial alpha diversity increased significantly along the time, while both temperature and plant species had a significant impact on the bacterial community, and plant type was shown to be the most important driving factor for the fungal community. The cosmopolitan bacterial taxa affiliated with Gammaproteobacteria, Bacteroidetes, Deltaproteobacteria, Firmicutes and Spirochaetes were key species in the investigated ecological networks, demonstrating significant co‐occurrence or co‐exclusion relationships with Basidiomycota and Ascomycota, according to different macrophyte species. This study indicates that bacteria involved in the decomposition of macrophyte leaf litter are more sensitive to temperature variance, and that fungi have a higher specificity to the composition of plant materials. The nutrient content of Hydrilla verticillata promoted a positive bacteria–fungi interaction, thereby accelerating the decomposition and re‐circulation of leaf litter.
Abstract
With recent methodological advances, molecular markers are increasingly used for semi-quantitative analyses of fungal communities. The aim to preserve quantitative relationships between ...genotypes through PCR places new demands on primers to accurately match target sites and provide short amplicons. The internal transcribed spacer (ITS) region of the ribosome encoding genes is a commonly used marker for many fungal groups. Here, we describe three new primers – fITS7, gITS7 and fITS9, which may be used to amplify the fungal ITS2 region by targeting sites in the 5.8S encoding gene. We evaluated the primers and compared their performance with the commonly used ITS1f primer by 454-sequencing of both artificially assembled templates and field samples. When the entire ITS region was amplified using the ITS1f/ITS4 primer combination, we found strong bias against species with longer amplicons. This problem could be overcome by using the new primers, which produce shorter amplicons and better preserve the quantitative composition of the template. In addition, the new primers yielded more diverse amplicon communities than the ITS1f primer.
Conidia are specialized structures produced at the end of the asexual life cycle of most filamentous fungi. They are responsible for fungal dispersal and environmental persistence. In pathogenic ...species, they are also involved in host recognition and infection. Conidial production, survival, dispersal, germination, pathogenicity and virulence can be strongly influenced by exposure to solar radiation, although its effects are diverse and often species dependent. UV radiation is the most harmful and mutagenic waveband of the solar spectrum. Direct exposure to solar radiation for a few hours can kill conidia of most fungal species. Conidia are killed both by solar UV-A and UV-B radiation. In addition to killing conidia, which limits the size of the fungal population and its dispersion, exposures to sublethal doses of UV radiation can reduce conidial germination speed and virulence. The focus of this review is to provide an overview of the effects of solar radiation on conidia and on the major systems involved in protection from and repair of damage induced by solar UV radiation. The efforts that have been made to obtain strains of fungi of interest such as entomopathogens more tolerant to solar radiation will also be reviewed.
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