The antibacterial activity and acting mechanism of hypocrellin A (HA) were conducted regarding in vitro activity of HA on Staphylococcus aureus GZ86 by analyzing the growth, permeability, and morphology of the bacterial cells following treatment with HA. The experimental results indicated 1.5 mg/l HA could completely inhibit the growth of 10⁷ CFU/ml S. aureus cells in liquid beef extract-peptone medium under a halogen-tungsten lamp for 120 min. Meanwhile, HA resulted in the leakage of reducing sugars and proteins and induced the respiratory chain dehydrogenases into inactive state, suggesting that HA were able to destroy the permeability of the bacterial membranes. When the cells of S. aureus were exposed to 2.5 mg/l HA under a halogen-tungsten lamp for 120 min, many pits and gaps were observed in bacterial cells by scanning electron microscopy, and the cell wall was fragmentary, indicating the bacterial cells were damaged severely. The experiments strongly confirmed the contribution of multiform reactive oxygen species (ROS) to bactericidal effect. In conclusion, the combined results suggested that ROS may damage the structure of bacterial cell wall and depress the activity of some membranous enzymes, which cause S. aureus bacteria to die eventually.
Seroepidemiology of Toxocara canis infection among adults of one ethnic Han and five aboriginal populations residing in mountainous areas of Taiwan was conducted by detecting serum IgG (>/=1:64) using a T. canis larval excretory-secretory antigen-based enzyme-linked immunosorbent assay. A short questionnaire interview was conducted to obtain data concerning their age, sex, occupation, consumption of raw pig liver, and possession of dogs. The overall seroprevalence (46.0%, 247 of 537) in the five aboriginal populations was significantly higher than that of ethnic Han population (30.2%, 13 of 43) (P = 0.04). Age, but not sex, seemed to be a factor related to positive serology. Aboriginal adults who had histories of eating raw pig liver (odds ratio [OR] = 1.65, P < 0.01), raising dogs (OR = 1.76, P < 0.01), or whose occupation was a laborer (OR = 1.78, P < 0.01) seemed to be more apt to be infected by T. canis than those without such histories and unemployed persons.
Aims: To investigate the effect of medium compositions and culture conditions on keratinase production by a novel thermophilic fungus Myceliophthora thermophila (Apinis) Oorschot strain GZUIFR‐H49‐1.
Methods and Results: The thermophilic strain GZUIFR‐H49‐1 with keratinolytic ability was characterized and identified as a strain of M. thermophila on the basis of its morphological characters and molecular analysis of ITS1‐5.8S‐ITS2 rDNA sequence. Among the medium compositions tested, the soluble starch (SS), urea, sodium thiosulfate and CaCl2 were the most effective C‐source, N‐source, S‐source and mineral ion, respectively, by employing the single‐factor experiment. The urea and pH value were the significant factors (P < 0·05) for the keratinase production in this experiment condition using Plackett–Burman factorial design. The conditions of keratinase production were further optimized by Box–Behnken design. Consequently, there was a 6·4‐fold increase (5100 U l−1) in the keratinase activity than the initial value (800 U l−1) by this optimal process.
Conclusions: This study indicated that the optimization design proved a useful and powerful tool for the development of optimal medium compositions and culture conditions. Myceliophthora thermophila strain GZUIFR‐H49‐1 was a promising fungus strain for keratinase production.
Significance and Impact of the Study: This study characterized a novel thermophilic M. thermophila strain GZUIFR‐H49‐1 with potential applications for keratinase production. These conditions of keratinase production obtained by means of optimization design will be accumulated as potential information for exploration and utilization to the new fungus isolate.
Securinega suffruticosa (Pall.) Rehd is an excellent natural secondary shrub in the Shell Islands of Yellow River Delta. The roots of S. suffruticosa have high medicinal value and are used to treat diseases, such as neurasthenia and infant malnutrition. Any organism that is isolated from this species is of immense interest due to its potential novel bioactive compounds. In this research, the distribution and diversity of culturable endophytic fungi in S. suffruticosa were studied, and the endophytic fungi with antimicrobial activity were screened. A total of 420 endophytic fungi isolates were obtained from the S. suffruticosa grown in Shell Islands, from which 20 genera and 35 species were identified through morphological and internal transcribed spacer (ITS) sequence analyses. Chaetomium, Fusarium, Cladosporium, and Ceratobasidium were the dominant genera. The high species richness S (42), Margalef index D 0 (5.6289), Shannon-Wiener index H 0 (3.1000), Simpson diversity index D s (0.9459), PIE index (0.8670), and evenness Pielou index J (0.8719) and a low dominant index λ (0.0541) indicated the high diversity of endophytic fungi in S. suffruticosa, the various species of endophytic fungi with obvious tissue specificity. The inhibition percentages of the 12 species of such endophytic fungi against Colletotrichum siamense were 3.6%-26.3%. C. globosum, Fusarium sp.3, and C. ramotenellum had a high antibacterial activity against Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) were between 0.5 mg/mL and 2 mg/mL. Alkaloid content detection indicated that endophytic fungi had a high alkaloid content, whereas the alkaloid contents of C. globosum and Fusarium sp.3 reached 0.231% and 0.170%, respectively. Members belonging to the endophytic fungal community in the S. suffruticosa of Shell Islands that may be used as antagonists and antibacterial agents for future biotechnology applications were identified for the first time.
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