The contamination of milk with aflatoxin M1 (AFM1), a possible carcinogen to humans, is a serious problem. In Thailand, there are few reports on AFM1 contamination in powdered milk. In this study, we investigated the occurrence of AFM1 in 79 commercial powdered milk products in Bangkok, Thailand over five years (2010–2014). An in-house immunoaffinity column-HPLC (IAC-HPLC) method was developed. Reconstituted powdered milk (10 mL) was applied to our IAC. The recoveries from 0.005–0.15 ng/mL AFM1-spiked reconstituted milk were 73.6–86.3% with 5.2–7.4% of RSD. Twelve samples (15%) were contaminated with 0.005–0.135 ng/mL of AFM1 (average 0.024 ng/mL, overall average 0.004 ng/mL) in reconstituted powdered milk. Our data indicated that the risk of AFM1 in commercial powdered milk in Bangkok, Thailand was sufficiently low.
Three topics from electron microscopic studies of microorganisms carried out in my laboratory in recent ten years are described. 1) Influenza A virus was observed in water by an ice-embedding method using phase contrast electron microscopy developed in Japan. Virions appeared as spherical or elongated particles consisting of spikes, an envelope, and a core with high contrast. 2) A new term the “structome” was introduced and defined as “the quantitative and three-dimensional structural information of a whole cell at electron microscopic level.” We performed structome analyses of Saccharomyces cerevisiae by using freeze-substitution and serial ultrathin sectioning electron microscopy. We found that there were one to four mitochondria and about 195,000 ribosomes in a cell. 3) In the deep-sea off the coast of Japan, we discovered a unique microorganism appearing to have cellular features intermediate between prokaryotes and eukaryotes. The organism, named as the Myojin parakaryote, was two orders of magnitude larger than a typical bacterium and had a large “nucleoid”, surrounded by a single layered “nucleoid membrane”, and bacteria-like “endosymbionts”, but it lacked mitochondria. This organism exemplifies a potential evolutionary path between prokaryotes and eukaryotes, and the presence of the organism supports the endosymbiotic theory for the origin of mitochondria and the karyogenetic hypothesis for the origin of the nucleus. These studies show that the electron microscopy is a powerful tool for studying a wide range of problems of microorganisms.
Because of the Great East Japan Earthquake (GEJE) and following turmoil including delay of the construction of temporary shelter, about 400,000 of Internal displaced people (IDP), victim of earthquake, tsunami and radiation problem, forced to live in the temporary evacuation centers for 9 months. Aiming not for prolonged stay, management of the living conditions, such as temperature and humidity, at temporary evacuation center has extremely difficult. It was easy to come up with the idea of deterioration of health condition of followed by changing of biological flora. Since this disaster happen, Primary Care for All Team organized by Japan Primary Care Association as a special unit to practice the humanitarian medical aid had been paying attention to the phenomenon of proliferation of molds and mites in temporary evacuation centers. Decision was made before the monsoon come. With technical and academic support from National Institute of Health Sciences (NIHS), team called “Myte/Mold Busters” was launch aimed for providing the cleaning service and sanitation activity to all the temporary evacuation center of Ishinomaki and Onagawa area. Quite few attentions have been paid for the health problem caused by mold in disaster and still we need more research and study about this area. However in GJEA, increase of the number of the patient complained about respiratory and skin symptoms were observed after the certain period of disaster. Furthermore, first case of severe symptom of respiratory failure related mold exposure was detected from the resident of temporary shelter which has been continuously followed by the research team of NIHS and revealed extremely high density of mold in their house. People have to live in harsh condition in evacuation center continuously in coming mega disaster such as Nankai Trough Earthquake and Tokyo Earth Quake. Climate of those areas are totally different. It will be more template and humid from that of Tohoku, appropriate condition for the mold. And still there are a lot of people living in temporary shelter in Tohoku. Health problem caused by mold in mega disaster are not yet paid so much attention from the public however, and so that’s why, we have to make effort to raise this issue to the public, develop counter major and prepare for the coming disaster as a pioneer in this field, to save the life, to help the people.
Aspergillus species (spp.) are medically important pathogens that cause aspergillosis, and A. fumigatus is the most prevalent causative agent of the disease. Aspergillus spp. produce various secondary metabolites; however, the role of these metabolites in aspergillosis remains unclear. Gliotoxin is a major secondary metabolite produced by A. fumigatus. Several recent studies have reported that gliotoxin contributes to the virulence of A. fumigatus. Here I review studies related to gliotoxin and its contribution to the infection caused by A. fumigatus.
Fungus is one of the major allergens such as mites and pollen. Especially, it is known that Kuro-koji molds sometimes causes occupational allergy of brewers. There is, however, no good diagnostic technology for fungal allergy. The inhomogeneous allergenic extract of fungi, which is caused by the biological diversity, makes it difficult to diagnose and treat fungal allergy. Although the identification of allergens is important to make fine allergenic extract, few fungal allergens were identified because many cumbersome steps are required to be identified allergens. Then, we attempted to develop the simple identification scheme for fungal allergen using bioinformatics technique. Some allergen candidates of Kuro-koji molds were successfully listed.
Fumonisin, a mycotoxin produced by some members of Fusarium fujikuroi species complex, causes swine pulmonary edema and equine leukoencephalomalacia. Clustering of the genes involving fumonisin biosynthesis in the genome have been revealed. The FUM cluster poses many questions in regard to the process obtained by Fusarium and its evolution. In this mini review, fumonisin characteristics are described and the role of fumonisin for the producing fungi and the evolution of the FUM cluster were discussed.
Fungal contamination of food is one of the most important food safety concerns, however effective techniques to prevent fungal contamination and/or control fungal growth in foods have not yet been established. Some endogenous volatile compounds in plants have antibacterial and/or antifungal activities. For example, when some plants are damaged, they release aliphatic aldehydes with six or nine carbons to protect themselves from microbial infection. Patulin is the major mycotoxin that contaminates apples and apple juice worldwide, and it is regulated in many countries. Patulin has been shown to be immunotoxic and neurotoxic by animal experiments. Many species of Penicillium and Aspergillus produce patulin, but P. expansum is the most typical species responsible for patulin contamination in apples. We attempted to assess the effects of aliphatic aldehydes on P. expansum. Aliphatic aldehydes composed of 3–6 carbons bearing an E double bond at the α-position completely inhibited the fungal growth and suppressed colony formation from spores at relatively low concentrations. On the basis of the structure-activity relationship, the antifungal activity of the compounds is probably attributable to the interaction of the aldehyde group with biological macromolecules. On the other hand, aliphatic aldehydes with 8–10 carbons stimulated patulin production by P. expansum. The results of a reverse transcription-quantitative polymerase chain reaction analysis suggested that the stimulation was partially due to enhanced transcription of some patulin biosynthetic genes. The effects of volatiles of apple on patulin production by P. expansum were also studied. Some volatile compounds, that is, 2-mehtylbutanoic acid and ethyl 2-methylbutanoate, were found to stimulate patulin production. These findings will contribute to the development of new techniques to prevent and control fungal and mycotoxin contamination of foods.
Phytopathogenic fungi Fusarium species are etiological agents of Fusarium head blight (FHB) and produce trichothecene mycotoxins such as deoxynivalenol (DON) and nivalenol (NIV) in cereals especially barley and wheat. Trichothecenes inhibit the protein synthesis in eukaryotic ribosomes. Therefore, trichothecene-contaminated cereals often cause foodborne illness such as immunosuprression, vomiting, and diarrhea in human and livestocks. Trichothecenes are also phytotoxins and act as effectors to promote infection in host plants. Based on visible disease symptoms, we selected 15 FHB-resistant lines of barley. When these resistant lines and susceptible controls were inoculated with conidia of F. asiaticum, the mycotoxin (NIV) contaminations of resistant two lines were less than half of those of susceptible controls. Furthermore, we performed comparative analysis of global gene expression profiles between these FHB-resistant (low NIV accumulation) lines vs. susceptible controls. A number of genes including the glutathione S-transferase (HvGST13) and glutathione reductase (HvGR2) were specifically up-regulated in the FHB-resistant lines. It is likely that these two genes are involved in the detoxification of NIV by NIV-GSH conjugation in barley. Therefore, we are studying these genes as candidates of trichothecene-detoxifing genes. This study may contributes to the understanding molecular mechanism of trichothecene detoxification in cereals.