Morphology and Molecular Analysis of Moesziomyces antarcticus Isolated From the Blood Samples of a Chinese Patient

Gut yeast diversity of Helicoverpa armigera (Lepidoptera: Noctuidae) under different dietary conditions

Yeast is one of the important symbiotic flora in the insect gut. However, little is known about the gut yeast in Helicoverpa armigera (Lepidoptera: Noctuidae) under various dietary conditions. The composition and function of the intestinal yeast community also remain unclear. In this research, we explored the composition of yeast microorganisms in H. armigera larvae under different feeding environments, including apple, pear, tomato, artificial diet (laboratory feeding), Urtica fissa, Helianthus annuus, and Zinnia elegans (wild environment) using high-throughput sequencing. Results showed that a total of 43 yeast OTU readings were obtained, comprising 33 yeast genera and 42 yeast species. The yeast genera with a total content of more than 5% were Hanseniaspora (36.27%), Moesziomyces (21.47%), Trichosporon (16.20%), Wickerhamomyces (12.96%) and Pichia (6.38%). Hanseniaspora was predominant when fed indoors with fruits, whereas Moesziomyces was only detected in the wild group (Urtica fissa, Helianthus annuus, Zinnia elegans) and the artificial diet group. After transferring the larvae from artificial diet to apple, pear and tomato, the composition of intestinal yeast community changed, mainly reflected in the increased relative abundance of Hanseniaspora and the decreased abundance of Trichosporon. Simultaneously, the results of α diversity index indicated that the intestinal yeast microbial diversity of H. armigera fed on wild plants was higher than that of indoor artificial feeding. PCoA and PERMANOVA analysis concluded that there were significant differences in the gut yeast composition of H. armigera larvae on different diets. Our results confirmed that gut yeast communities of H. armigera can be influenced by host diets and may play an important role in host adaptation.

Kj-mhpC Enzyme in Klebsiella jilinsis 2N3 Is Involved in the Degradation of Chlorimuron-Ethyl via De-Esterification

Microbial degradation is a highly efficient and reliable approach for mitigating the contamination of sulfonylurea herbicides, such as chlorimuron-ethyl, in soil and water. In this study, we aimed to assess whether Kj-mhpC plays a pivotal role in the degradation of chlorimuron-ethyl. Kj-mhpC enzyme purified via prokaryotic expression exhibited the highest catalytic activity for chlorimuron-ethyl at 35 °C and pH 7. Bioinformatic analysis and three-dimensional homologous modeling of Kj-mhpC were conducted. Additionally, the presence of Mg+ and Cu2+ ions partially inhibited but Pb2+ ions completely inhibited the enzymatic activity of Kj-mhpC. LC/MS revealed that Kj-mhpC hydrolyzes the ester bond of chlorimuron-ethyl, resulting in the formation of 2-(4-chloro-6-methoxypyrimidine-2-amidoformamidesulfonyl) benzoic acid. Furthermore, the point mutation of serine at position 67 (Ser67) confirmed that it is the key amino acid at the active site for degrading chlorimuron-ethyl. This study enhanced the understanding of how chlorimuron-ethyl is degraded by microorganisms and provided a reference for bioremediation of the environment polluted with chlorimuron-ethyl.

High-quality genome resource of a basidiomycetous yeast, Moesziomyces antarcticus isolate RS1, isolated from rice seed

Moesziomyces antarcticus (anamorph: Pseudozyma antarctica) is a basidiomycetous yeast in the Ustilaginaceae family and is a core member of the rice seed microbiome. M. antarcticus RS1 was isolated from surface-sterilized rice seeds. This 18.287 Mb draft genome of M. antarcticus RS1 is comprised of a 60.8% GC content and 6,817 protein-coding genes.

A case of Moesziomyces antarcticus peritonitis in a patient undergoing peritoneal dialysis

Background

Fungal peritonitis is a common and serious complication associated with peritoneal dialysis (PD), and it is often refractory to treatment.

Case presentation

A 70-year-old patient undergoing peritoneal dialysis was admitted to our hospital with fever and cloudy PD fluid. A diagnosis of yeast-like fungal peritonitis was made by examining the PD fluid. After starting intravenous caspofungin acetate, the PD catheter was removed. A fungal pathogen was isolated from the peritoneal fluid and identified as Cryptococcus sp. Based on the results of antifungal susceptibility testing, the treatment was changed to oral voriconazole and continued for 6 weeks. However, because of the discrepancy between the morphological findings and culture results, we performed genetic analysis, which uncovered Moesziomyces antarcticus. This patient was diagnosed with PD-related peritonitis caused by M. antarcticus and was successfully treated with voriconazole and removal of the PD catheter.

Conclusions

Reports of human infection by M. antarcticus are rare, and only two cases have been recognized. This may be the first case of infection detected in PD fluid.

A Novel Pathway of Chlorimuron-Ethyl Biodegradation by Chenggangzhangella methanolivorans Strain CHL1 and Its Molecular Mechanisms

Chlorimuron-ethyl is a widely used herbicide in agriculture. However, uncontrolled chlorimuron-ethyl application causes serious environmental problems. Chlorimuron-ethyl can be effectively degraded by microbes, but the underlying molecular mechanisms are not fully understood. In this study, we identified the possible pathways and key genes involved in chlorimuron-ethyl degradation by the Chenggangzhangella methanolivorans strain CHL1, a Methylocystaceae strain with the ability to degrade sulfonylurea herbicides. Using a metabolomics method, eight intermediate degradation products were identified, and three pathways, including a novel pyrimidine-ring-opening pathway, were found to be involved in chlorimuron-ethyl degradation by strain CHL1. Transcriptome sequencing indicated that three genes (atzF, atzD, and cysJ) are involved in chlorimuron-ethyl degradation by strain CHL1. The gene knock-out and complementation techniques allowed for the functions of the three genes to be identified, and the enzymes involved in the different steps of chlorimuron-ethyl degradation pathways were preliminary predicted. The results reveal a previously unreported pathway and the key genes of chlorimuron-ethyl degradation by strain CHL1, which have implications for attempts to enrich the biodegradation mechanism of sulfonylurea herbicides and to construct engineered bacteria in order to remove sulfonylurea herbicide residues from environmental media.

Detection and diversity of the mannosylerythritol lipid (MEL) gene cluster and lipase A and B genes of Moesziomyces antarcticus isolated from terrestrial sites chronically contaminated with crude oil in Trinidad

BACKGROUND

Mannosylerythritol lipids (MELs) belong to the class of glycolipid biosurfactants and are produced by members of the Ustilago and Moesziomyces genera. Production of MELs is regulated by a biosynthetic gene cluster (MEL BGC). Extracellular lipase activity is also associated with MEL production. Most microbial glycolipid-producers are isolated from oil-contaminated environments. MEL-producing yeast that are capable of metabolizing crude oil are understudied, and there is very limited data on indigenous strains from tropical climates. Analysis of the MEL BGC and lipase genes in Trinidad M. antarcticus strains, using a gene-targeted approach, revealed a correlation between their intrinsic capability to degrade crude oil and their adaptation to survive in a chronically polluted terrestrial environment.

RESULTS

M. antarcticus was isolated from naturally-occurring crude oil seeps and an asphaltic mud volcano in Trinidad; these are habitats that have not been previously reported for this species. Genus identification was confirmed by the large-subunit (LSU) and the small-subunit (SSU) sequence comparisons and species identification was confirmed by ITS sequence comparisons and phylogenetic inference. The essential genes (Emt1, Mac1, Mac2, Mmf1) of the MEL BGC were detected with gene-specific primers. Emt1p, Mac1p and Mmf1p sequence analyses confirmed that the Trinidad strains harboured novel synonymous amino acid (aa) substitutions and structural comparisons revealed different regions of disorder, specifically for the Emt1p sequence. Functionality of each protein sequence was confirmed through motif mining and mutation prediction. Phylogenetic relatedness was inferred for Emt1p, Mac1p and Mmf1p sequences. The Trinidad strains clustered with other M. antarcticus sequences, however, the representative Trinidad M. antarcticus sequences consistently formed a separate, highly supported branch for each protein. Similar phylogenetic placement was indicated for LipA and LipB nucleotide and protein sequences. The Trinidad strains also demonstrated lipolytic activity in culture, with an ability to utilize different carbon sources. Comparative evolution of MEL BGC and LipA gene suggested early and late duplication events, depending on the gene, followed by a number of speciation events within Ustilaginaceae. M. antarcticus and M. aphidis were separated from all other members of Ustilaginaceae and two gene homologues were detected, one for each species.

CONCLUSIONS

Sequence analyses was based on a novel gene-targeted approach to analyze the essential genes of the MEL BGC and LipA and LipB genes of M. antarcticus strains from Trinidad. The findings indicated that these strains accumulated nucleotide mutations to a threshold level that did not affect the function of specific proteins encoded by the MEL BGC and LipA and LipB genes. The biosurfactant and lipase enzymes secreted by these Trinidad M. antarcticus strains facilitated their survival in oil-contaminated terrestrial environments. These findings suggest that the Trinidad strains should be explored as promising candidates for the commercial production of MEL biosurfactants and lipase enzymes.

First Case of Subcutaneous Mycoses Caused by Dirkmeia churashimaensis and a Literature Review of Human Ustilaginales Infections

Objective

Dirkmeia churashimaensis, belonging to Ustilaginales fungi, has never been reported as clinical pathogenic until very recently. In this study, we report an unusual subcutaneous infection with Dirkmeia churashimaensis and reviewed all human Ustilaginales infections. The aim is to better understand their epidemiology, infection type, risk factors, and the sensitivity to antifungal agents.

Methods

An 80-year-old female farmer developed extensive plaques and nodules on her left arm within 2 years. Pathological and microbiological examinations identified a new pathological agent, Dirkmeia churashimaensis, as the cause of this infection. The patient was successfully cured by oral itraconazole. We reviewed a total of 31 cases of Ustilaginales cases, among of which only three were skin infections.

Results

Local barrier damage (i.e., surgery, trauma, and basic dermatosis) and systemic immunodeficiency (i.e., preterm and low birthweight, Crohn’s disease, malignant cancer, and chemotherapy) are risk factors for Ustilaginales infection. The D1/D2 and ITS regions are the frequently used loci for identifying the pathogens together with phenotype. Most patients could survive due to antifungal treatment, whereas seven patients died. Amphotericin B, posaconazole, itraconazole, and voriconazole showed good activity against these reported strains, whereas fluconazole, 5-flucytosine, and echinocandins usually showed low susceptibility. Itraconazole had good efficiency for subcutaneous infections.

Conclusions

The present case study and literature review reveal that Ustilaginales can be opportunistic pathogenic normally in immunocompromised and barrier damage people. A proper identification of fungi can be crucial for clinical treatment, and more data of antifungal are needed for choice of medication against this kind of infections.

Prevalence and in vitro antifungal susceptibility of commensal yeasts in the external ear canal of cats

Background

Lifestyle factors such as hair length, the frequency of ear cleaning and bathing, age, cat rearing, and sex may contribute to opportunistic yeast infections in the external ear canal of cats. This study aimed to determine the prevalence of commensal yeast organisms in cats’ external ear canals, evaluate their predisposing lifestyle factors, and test the susceptibility of Malassezia pachydermatis to antifungal agents.

Results

A total of 53 cats (33 male and 20 female) seronegative for feline leukemia virus and feline immunodeficiency virus were enrolled in this study. Their mean age (± standard deviation) was 6.04 (± 3.49) years. Fungal cultures and polymerase chain reaction tests were performed to identify the yeast species derived from the external ear canal. The association between lifestyle factors and the presence of M. pachydermatis was evaluated using Fisher’s exact test. The susceptibility of M. pachydermatis to antifungal agents was also analyzed. M. pachydermatis was the most frequently recovered yeast species, with a prevalence of 50.94 % (95 % confidence interval [CI]: 36.84–64.94 %). There was an association between hair length and a positive culture for M. pachydermatis (p = 0.0001). The odds of a negative culture for M. pachydermatis among short-haired cats was 11.67 (95 % CI, 3.22–42.24) times higher than that among long-haired cats (p = 0.0002). There was also an association between the frequency of ear cleaning and the presence of M. pachydermatis (p = 0.007). The odds of a negative culture for M. pachydermatis in cats that were receiving ear cleaning at intervals of ≤ 2 weeks was 5.78 (95 % CI, 1.67–19.94) times greater than that of cats receiving ear cleaning at intervals greater than 2 weeks or never (p = 0.0055). Ranges of minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations for itraconazole, ketoconazole, miconazole, and terbinafine against M. pachydermatis were ≤ 0.063–4 and ≤ 0.063–≥32, ≤ 0.063–8 and 0.125–≥32, ≤ 0.063–≥32 and 0.5–≥32, and ≤ 0.016–1 and 0.125–8 µg/ml, respectively.

Conclusions

M. pachydermatis was the most commonly identified yeast organism in the external ear canal of healthy cats. Hair length and the frequency of ear cleaning played a role in the colonization of M. pachydermatis. The M. pachydermatis isolates had various MIC levels for common fungicides.

Diversity and Oil Degradation Potential of Culturable Microbes Isolated from Chronically Contaminated Soils in Trinidad

Trinidad and Tobago is the largest producer of oil and natural gas in Central America and the Caribbean. Natural crude oil seeps, in addition to leaking petroleum pipelines, have resulted in chronic contamination of the surrounding terrestrial environments since the time of petroleum discovery, production, and refinement in Trinidad. In this study, we isolated microbes from soils chronically contaminated with crude oil using a culture-dependent approach with enrichment. The sampling of eight such sites located in the southern peninsula of Trinidad revealed a diverse microbial composition and novel oil-degrading filamentous fungi and yeast as single-isolate degraders and naturally occurring consortia, with specific bacterial species not previously reported in the literature. Multiple sequence comparisons and phylogenetic analyses confirmed the identity of the top degraders. The filamentous fungal community based on culturable species was dominated by Ascomycota, and the recovered yeast isolates were affiliated with Basidiomycota (65.23%) and Ascomycota (34.78%) phyla. Enhanced biodegradation of petroleum hydrocarbons is maintained by biocatalysts such as lipases. Five out of seven species demonstrated extracellular lipase activity in vitro. Our findings could provide new insights into microbial resources from chronically contaminated terrestrial environments, and this information will be beneficial to the bioremediation of petroleum contamination and other industrial applications.

Carboxylesterase, a de-esterification enzyme, catalyzes the degradation of chlorimuron-ethyl in Rhodococcus erythropolis D310-1

Microbial degradation is considered to be the most acceptable method for degradation of chlorimuron-ethyl, a typical long-term residual sulfonylurea herbicide, but the underlying mechanism at the genetic and biochemical levels is unclear. In this work, the genome sequence of the chlorimuron-ethyl-degrading bacterium Rhodococcus erythropolis D310-1 was completed, and the gene clusters responsible for the degradation of chlorimuron-ethyl in D310-1 were predicted. A carboxylesterase gene, carE, suggested to be responsible for carboxylesterase de-esterification, was cloned from D310-1. CarE was expressed in Escherichia coli BL21 and purified to homogeneity. The active site of the chlorimuron-ethyl-degrading enzyme CarE and the biochemical activities of CarE were elucidated. The results demonstrated that CarE is involved in catalyzing the de-esterification of chlorimuron-ethyl. A carE deletion mutant strain, D310-1ΔcarE, was constructed, and the chlorimuron-ethyl degradation rate in the presence of 100 mg L^-1 chlorimuron-ethyl within 120 h decreased from 86.5 % (wild-type strain D310-1) to 58.2 % (mutant strain D310-1ΔcarE). Introduction of the plasmid pNit-carE restored the ability of the mutant strain to utilize chlorimuron-ethyl. This study is the first to demonstrate that carboxylesterase can catalyze the de-esterification reaction of chlorimuron-ethyl and provides new insights into the mechanism underlying the degradation of sulfonylurea herbicides and a theoretical basis for the utilization of enzyme resources.