Toxin-producing endosymbionts shield pathogenic fungus against micropredators

The phytopathogenic fungus Rhizopus microsporus harbours a bacterial endosymbiont (Mycetohabitans rhizoxinica) for the production of the toxin rhizoxin, the causative agent of rice seedling blight. This toxinogenic bacterial-fungal alliance is, however, not restricted to the plant disease, but has been detected in numerous environmental isolates from geographically distinct sites covering all five continents. Yet, the ecological role of rhizoxin beyond rice seedling blight has been unknown. Here we show that rhizoxin serves the fungal host in fending off protozoan and metazoan predators. Fluorescence microscopy and co-culture experiments with the fungivorous amoeba Protostelium aurantium revealed that ingestion of R. microsporus spores is toxic to P. aurantium. This amoebicidal effect is caused by the bacterial rhizoxin congener rhizoxin S2, which is also lethal towards the model nematode Caenorhabditis elegans. By combining stereomicroscopy, automated image analyses, and quantification of nematode movement we show that the fungivorous nematode Aphelenchus avenae actively feeds on R. microsporus that is lacking endosymbionts, while worms co-incubated with symbiotic R. microsporus are significantly less lively. This work uncovers an unexpected ecological role of rhizoxin as shield against micropredators. This finding suggests that predators may function an evolutionary driving force to maintain toxin-producing endosymbionts in non-pathogenic fungi.

Assessing the Fungal Simultaneous Removal Efficiency of Carbamazepine, Diclofenac and Ibuprofen in Aquatic Environment

Unused pharmaceutical compounds (PhCs) discharged into the aquatic environment have been regarded as emerging pollutants due to potential harmful effects on humans and the environment. Microbial bioremediation is considered as a viable option for their removal from wastewater. The aim of this study was to assess the simultaneous removal of carbamazepine (CBZ), diclofenac (DCF) and ibuprofen (IBP) by previously isolated fungi (Aspergillus niger, Mucor circinelloides, Trichoderma longibrachiatum, Trametes polyzona, and Rhizopus microsporus). The tolerance to PhCs was conducted by tracking the fungal mycelium mat diameters in solid media and its dry biomass in liquid media, at the drug concentration range of 0.1 to 15 mg/L. The fungal enzymatic activities were determined for lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac), respectively. The PhC removal efficiency of the fungi was assessed in aerated batch flasks and the drug concentrations and intermediate compounds formation were determined by using SPE-UPLC/MS. A tolerance over 70% was recorded for all the fungi at drug concentration of 0.1 mg/L. Manganese peroxidase was produced by all the fungi with very low amount of LiP, while all the enzymes were produced by T. polyzona. The pH of 4.3, temperature 37 ± 1.5°C and incubation time of 6 days were the optimum parameters for the fungal enzymatic activities. The best removal of CBZ (87%) was achieved by R. microsporus after 10 days. Between 78 and 100% removal of DCF was observed by all the fungi after 24 h, while 98% of IBP was removed after 2 days by M. circinelloides. Only a few intermediate compounds were identified after 3 days and disappeared after 10 days of incubation. This study demonstrated that apart from the basidiomycetes, the ascomycetes and zygomycetes are also producers of ligninolytic enzymes and have the ability to biodegrade emerging pollutants such as PhCs.

Extração de óleos essenciais do Caryocar Coriaceum (pequi) por vias enzimáticas

A espécie Caryocar Coriaceum (pequi), como é popularmente conhecida, é um fruto que em algumas regiões é bastante utilizado na culinária popular brasileira. Além de possuir um gosto peculiar, o óleo extraído do fruto traz benefícios a saúde sendo muito utilizado na medicina popular. Frente ao exposto, este estudo apresentou como objetivo analisar, através de experimento com abordagem qualitativa, a viabilidade econômica da extração de óleos essenciais de pequi por via enzimática. Através da suspensão do fungo, Rhizopus Microsporus, foi estabelecido o melhor tempo de fermentação de 72 horas e a atividade hidrolítica mais eficiente para que através do extrato multienzimático da celulase fosse realizado a técnica de extração do óleo do pequi. Após a realização de todas estas etapas para obtenção do óleo, seja por meio de enzimas ou água, observou-se que a enzima, Rhizopus Microsporus, possui uma grande atividade para a extração do óleo essencial do pequi, quando se compara a hidodestilação somente com o óleo e água. Dessa forma, a utilização do fungo filamentoso, Rhizopus Microsporus, pode ser uma alternativa viável na extração de óleos essenciais, tornando o processo mais econômico por reduzir o tempo de extração e a energia do processo e ser ambientalmente correto, ou seja, tornou o processo da extração do óleo menor, visto que, com a enzima amplia essa extração.

Successful treatment of pulmonary mucormycosis caused by Rhizopus microsporus with posaconazole

Background Mucormycosis is a rare fungal infection occurring chiefly in the lung or the rhino-orbital-cerebral compartment, particularly in patients with immunodeficiency or diabetes mellitus. Among Mucorales fungi, Rhizopus spp. are the most common cause of mucormycosis. Case presentation We report a case of pulmonary mucormycosis caused by Rhizopus microsporus in a young patient with diabetes but no other apparent risk factors. The diagnosis mainly relied on clinical manifestation, positive pulmonary tissue biopsy, and fungal culture. The patient was successfully treated with posaconazole oral suspension and remains asymptomatic at one-year follow-up. Conclusions Pulmonary mucormycosis is a life-threatening condition and posaconazole is an effective treatment for pulmonary mucormycosis caused by Rhizopus microspores.

Case Report: Metagenomics Next-Generation Sequencing Can Be Performed for the Diagnosis of Disseminated Mucormycosis

Mucormycosis is an infection caused by a group of filamentous molds with in the order Mucorales. In developing countries, most cases of mucormycosis occur in persons with poorly controlled diabetes mellitus or subjects with normal post-traumatic immune function. Mucormycosis exhibits a marked propensity for invading blood vessels. The mortality rate of invasive mucormycosis is very high (>30–50%), and 90% of mortality is related to disseminated diseases. We report a 62-year-old man with underlying diseases, such as diabetes and psoriatic arthritis, with a history of trauma before admission. Chest CT showed multiple cavities. Based on the suspected clinical manifestation of mucormycosis infection, the patient received a microbiological culture of bronchoalveolar lavage fluid, and metagenomics next generation sequencing (mNGS) was performed. The results suggested Klebsiella pneumoniae infection. However, Rhizopus microsporus strains were shown by the mNGS of transpulmonary puncture tissue. Therefore, we report a case in which rare pathogens are identified by mNGS.

DOMESTICATION AND FORMULATION OF RHIZOPODOPSIS JAVENSIS AS A TEMPEH STARTER

ABSTRACT Domestication of wild fungal strains involved in the manufacture of traditional fermented foods often occurs spontaneously. Rhizopodopsis javensis (Rh. javensis) is taxonomically close to Rhizopus. The wild strain Rhizopodopsis javensis has found in cool climates can be developed as a starter in tempeh production in temperate regions. Before formulating it as a tempeh starter, a wild strain of Rh. javensis needs to be domesticated in human-made niches. A wild strain of Rh. javensis was domesticated by subculture using rice flour media at optimum growth temperature and carried out every five days. The spore's density and viability and the starter's water content were used to determine its quality. The results showed that Rh. javensis grew optimally at 22 ℃. With seven-time subcultures using rice flour media, the domestication process did not change the Rh. javensis growth rate and colony appearance. The growth rate of Rh. javensis is relatively the same as that of commercial tempeh starter and pure R. microsporus var. oligosporus, at each optimal growth temperature. In the rice flour media as a carrier, Rh. javensis produces spore's density that is relatively the same as that of commercial tempeh starter but with lower spore's viability and higher water content. Therefore, Rh. javensis cannot be used as a starter to produce tempeh in the temperate region. The carrier material and drying processes still need to be modified to increase spore viability and improve the overall quality, including the starter's lifespan. Keywords: food fermentation, Rhizopus microsporus var. oligosporus, spore's viability, starter quality, wild strain ABSTRAK Domestikasi galur liar kapang yang terlibat dalam dalam pembuatan makanan fermentasi tradisional, sering terjadi secara spontan. Rhizopodopsis javensis (Rh. javensis) merupakan salah satu galur liar kapang yang memiliki hubungan taksonomi dekat dengan Rhizopus. Strain liar ini ditemukan di daerah beriklim sejuk, sehingga berpotensi untuk dikembangkan sebagai starter tempe untuk produksi di daerah beriklim sedang. Untuk mendapatkan kultur yang tumbuh subur di relung (niches) buatan manusia, strain liar Rh. javensis perlu didomestikasi terlebih dahulu. Penelitian ini bertujuan untuk mendomestikasi strain Rh. javensis liar yang dilanjutkan dengan memformulasikannya sebagai starter tempe. Domestikasi dilakukan dengan menumbuhkan strain liar Rh. javensis pada media tepung beras pada suhu pertumbuhan optimum dan diulangi setiap lima hari. Kerapatan dan viabilitas spora, serta kadar air starter digunakan sebagai penilaian keberhasilan starter. Hasil penelitian menemukan Rh. javensis tumbuh optimal pada suhu 22 ℃. Domestikasi dengan cara subkultur koloni Rh. javensis pada media tepung beras selama 7 kali tidak mengubah kecepatan pertumbuhan Rh. javensis dan penampakan koloni. Laju pertumbuhan Rh. javensis relatif sama dengan laju pertumbuhan starter tempe komersial dan R. microsporus var. oligosporus murni, pada suhu optimum pertumbuhan masing-masing. Formulasi tepung beras sebagai media pembawa starter Rh. javensis, menghasilkan kerapatan spora yang relatif sama dengan starter tempe komersial, namun viabilitas sporanya rendah dan kadar airnya tinggi. Starter Rh. javensis belum dapat digunakan untuk membuat tempe. Substrat dan proses pengeringan masih perlu dimodifikasi untuk meningkatkan viabilitas spora dan kualitas starter tempe secara keseluruhan, termasuk umur simpan starter. Keywords: fermentasi makanan, kualitas starter, Rhizopus microsporus var. oligosporus, strain liar, viabilitas spora

A Case Series of Pulmonary Mucormycosis Caused by Rhizopus Microsporus

Mucormycosis is a relatively uncommon but intractable fungal infectious disease. The mortality is very high when it occurs. In this study, we reported a continuous cases of pulmonary mucormycosis in three patients who suffered from chronic kidney disease, history of renal transplantation and multiple myeloma in April 2017, respectively. Cultures were obtained from several specimens (pathological tissue, bronchoalveolar lavage fluid and sputum) and all identified as Rhizopus microsporus by Matrix-Assisted Laser Desorption Ionization Time- Of-Flight (MALDI-TOF) mass spectrometry and ITS DNA sequencing methods. In addition, they all showed susceptibility to amphotericin B and posaconazole. Unfortunately, even through the three patients all treated with amphotericin B and posaconazole, one man still died eventually. Clinicians should keep an eye on patients who are at high risk of acquiring this fatal disease and make early intervention strategies to reduce terrible outcomes.