Genetic and Chemical Diversity of Edible Mushroom Pleurotus Species

The genus Pleurotus is one of the most widely cultivated and edible mushrooms with various cultivators. Three molecular characteristics were used to evaluate the genetic diversity of 132 tested samples. Phylogenetic analysis showed five clades for tested samples of the genus Pleurotus by the combined ITS and LSU sequences with strong bootstraps and Bayesian posterior probability supports. A total of 94 polymorphic fragments ranging from 10 to 100 bp were observed by using an intersimple sequence repeat (ISSR) marker. The DNA fragment pattern showed that P. ostreatus cultivator (strain P9) was clearly distinguished from wild strain based on their clear banding profiles produced. DNA GC content of the genus Pleurotus varied from 55.6 mol% to 43.3 mol%. Their chemical composition was also determined, including sugar, amino acid, polar lipid, mycolic acid, quinone, and fatty acid, which presented some high homogeneity. Most of the tested samples contained mycolic acid; glucose and arabinose as the main sugars; aspartic acid, arginine, lysine, tyrosine, and alanine as the main amino acids; and C16:0, C18:0, C18:2cis-9,12, anteiso-C14:0, and summed feature 8 as the main fatty acids. In addition, their polar lipid profiles were investigated for the first time, which significantly varied among Pleurotus species. The genus Pleurotus contained menaquinone-6 as the sole respiratory quinone, which showed a significant difference with that of its closely related genera. These results of this study demonstrated that the combined method above could efficiently differentiate each Pleurotus species and thus be considered an efficient tool for surveying the genetic diversity of the genus Pleurotus.

Immunity acquired by a minority active fraction of the population could explain COVID-19 spread in Greater Buenos Aires (June-November 2020)

The COVID-19 pandemic had an uneven development in different countries. In Argentina, the pandemic began in march 2020 and, during the first 3 months, the vast majority of cases were concentrated in a densely populated region that includes the city of Buenos Aires (country capital) and the Greater Buenos Aires area that surrounds it. This work focuses on the spread of COVID-19 between June and November 2020 in Greater Buenos Aires. Within this period of time there was no vaccine, basically only the early wild strain of SARS-CoV-2 was present, and the official restriction and distancing measures in this region remained more or less constant. Under these particular conditions, the incidences show a sharp rise from June 2020 and begin to decrease towards the end of August until the end of November 2020. In this work we study, through mathematical modelling and available epidemiological information, the spread of COVID-19 in this region and period of time. We show that a coherent explanation of the evolution of incidences can be obtained assuming that only a minority fraction of the population got involved in the spread process, so that the incidences decreased as this group of people was becoming immune. The observed evolution of the incidences could then be a consequence at the population level of lasting immunity conferred by SARS-CoV-2.

Enhancement of membrane vesicle production by disrupting the degP gene in Meiothermus ruber H328

The phenomenon of membrane vesicle (MV) production is known to be common to all bacterial cells. Although MVs are expected to be employed in a variety of applications, improving MV productivity is essential for applications. Since the deletion of the degP gene, a periplasmic dual-function protease and chaperone, in Escherichia coli has successfully improved MV production capacity, we tried to enhance MV productivity in the thermophilic M. ruber H328 by deleting the degP gene. One gene (mrH_0331) was selected for degP gene from the H328 genome and we constructed the mutant strain ∆degP by deleting the degP gene of the H328 strain that was replaced with the htk gene showing thermophilic kanamaycin resistance by homologous recombination. The mutant strain ∆degP exhibited smooth growth but a lower level of turbidity at 60 °C although there was no difference in growth at 55 °C between the wild strain and the mutant strain. Finally, we have confirmed that incubation at 60 °C increases MV in the mutant strain ∆degP strain about fivefold by using two fluorescent dyes, DiI and FM4-64, which is followed by TEM analysis. The deletion of the degP gene presumably causes an increase in denatured proteins at 60 °C, leading to enhanced MV production. Meanwhile, the S-layer protein included in the outer membrane of the H328 strain increased in the MV fraction prepared from the mutant cells incubated at 60 °C. This indicates that this method is effective for MV production and that degP deletion enhances it in strain H328.

New Investigations with Lupane Type A-Ring Azepane Triterpenoids for Antimycobacterial Drug Candidate Design

Twenty lupane type A-ring azepano-triterpenoids were synthesized from betulin and its related derivatives and their antitubercular activity against Mycobacterium tuberculosis, mono-resistant MTB strains, and nontuberculous strains Mycobacterium abscessus and Mycobacterium avium were investigated in the framework of AToMIc (Anti-mycobacterial Target or Mechanism Identification Contract) realized by the Division of Microbiology and Infectious Diseases, NIAID, National Institute of Health. Of all the tested triterpenoids, 17 compounds showed antitubercular activity and 6 compounds were highly active on the H37Rv wild strain (with MIC 0.5 µM for compound 7), out of which 4 derivatives also emerged as highly active compounds on the three mono-resistant MTB strains. Molecular docking corroborated with a machine learning drug-drug similarity algorithm revealed that azepano-triterpenoids have a rifampicin-like antitubercular activity, with compound 7 scoring the highest as a potential M. tuberculosis RNAP potential inhibitor. FIC testing demonstrated an additive effect of compound 7 when combined with rifampin, isoniazid and ethambutol. Most compounds were highly active against M. avium with compound 14 recording the same MIC value as the control rifampicin (0.0625 µM). The antitubercular ex vivo effectiveness of the tested compounds on THP-1 infected macrophages is correlated with their increased cell permeability. The tested triterpenoids also exhibit low cytotoxicity and do not induce antibacterial resistance in MTB strains.

Artificial cultivation of a novel wild strain of Lepista sordida (Sowerby) Pat from south west China

A novel wild strain of Lepista sordida mushroom was collected from a soybean field in Liujiaba at Dazhou district of south western area of China in 2015.The morphological description and molecular identification were conducted to confirm the species. In the present study, optimization was carried out from mycelial growth and fruit body production. For DAAS-E70, the best growth rate was obtained using yeast malt extract, pH 6.0 and temperature 25°C. The wheat grain mushroom spawn was used for upscaling of the mycelium to be used for fruiting body production. In the field experiments, the average biological efficiency of DAAS-E70 was higher than that of Jilin-1, in which, DAAS-E70 accounting for 41.22% of the average biological efficiency, while the Jilin-1 was 35.02%. The stable biological efficiency of DAAS-E70 in different environments and seasons showed that the DAAS-E70 could be used for its commercial cultivation and could provide a new reference for its artificial domestication. Bangladesh J. Bot. 50(3): 813-818, 2021 (September) Special

Biodegradation of Nodularin by a Microcystin-Degrading Bacterium: Performance, Degradation Pathway, and Potential Application

Currently, studies worldwide have comprehensively recognized the importance of Sphingomonadaceae bacteria and the mlrCABD gene cluster in microcystin (MC) degradation. However, knowledge about their degradation of nodularin (NOD) is still unclear. In this study, the degradation mechanism of NOD by Sphingopyxis sp. m6, an efficient MC degrader isolated from Lake Taihu, was investigated in several aspects, including degradation ability, degradation products, and potential application. The strain degraded NOD of 0.50 mg/L with a zero-order rate constant of 0.1656 mg/L/d and a half-life of 36 h. The average degradation rate of NOD was significantly influenced by the temperature, pH, and initial toxin concentrations. Moreover, four different biodegradation products, linear NOD, tetrapeptide H-Glu-Mdhb-MeAsp-Arg-OH, tripeptide H-Mdhb-MeAsp-Arg-OH, and dipeptide H-MeAsp-Arg-OH, were identified, of which the latter two are the first reported. Furthermore, the four mlr genes were upregulated during NOD degradation. The microcystinase MlrA encoded by the mlrA gene hydrolyzes the Arg-Adda bond to generate linear NOD as the first step of NOD biodegradation. Notably, recombinant MlrA showed higher degradation activity and stronger environmental adaptability than the wild strain, suggesting future applications in NOD pollution remediation. This research proposes a relatively complete NOD microbial degradation pathway, which lays a foundation for exploring the mechanisms of NOD degradation by MC-degrading bacteria.

Overview of Some Factors Affecting the Durability and Efficacy of LLINs Used by the Communities in South Region of Cameroon, Central Africa

Background: Long-lasting insecticidal nets (LLINs) are widely used in sub-Saharan Africa to control the transmission of malaria parasites by Anopheles mosquitoes. However, their operational lifespan depends on numerous factors that are often not considered. This paper investigates on some of the factors likely associated with the rapid breakdown of LLINs efficacy in urban and rural settings of the seaport city of Kribi, South Region of Cameroon. Methods: A cross-sectional survey was conducted in June 2019 including: (i) a household survey using standard questionnaire for brands of LLINs used, their maintenance, and coverage rates in study communities, (ii) assessment of the physical integrity of nets, and (iii) WHO cone bioassays to determine the residual efficacy of the nets against wild strains and susceptible reference laboratory strains of Anopheles gambiae s. l. species. Results: A total of 540 households were surveyed, 235 in Kribi- urban and 305 in Kribi-rural. The overall net coverage rate per sleeping space was 68.82%, irrespectively with a similar trend between Kribi-rural (68.98%) and Kribi-urban (68.62%) (p = 0.929). Of the 1,211 LLINs recorded, 64.73% were Interceptor®, 25.44% were PermaNet®, 4.68% were Olyset Net ; the remainder (05.13%) belonged to Yorkool®, Royal Sentry®, Netto®, Super Net® and Panda Net®. The hole indices were significantly correlated to the frequency of washes in kribi-urban as well as kribi-rural settings (p≤ 10-3). Nets washed with ordinary soap had lower hole indices compared to nets washed with corrosive detergents in the two groups of settings in the study area (p≤ 10-4). Likewise, nets dried under the sun significantly recorded a higher hole indices compared to nets dried in a shaded area (p≤ 0.04) in the two groups of settings. Polyethylene fibers were significantly less degraded than polyester fibers. The bio efficacy results revealed 21.6% - 99.6% mortality rates of the Kisumu strain exposed to LLINs washed more than 20 times and from 0.8% to 76.50% for the wild strain. LLINs washed with ordinary soap significantly retained their lethal properties more than LLINs washed with corrosive detergents (p=10-4). Similarly, LLINs dried in the shade retained their lethal properties more than those spread in the sun.Conclusion: Excessive washes, Corrosive detergents and drying regimes are factors that degrade the toxic effect of insecticide impregnated on LLINs. Awareness campaigns are needed to encourage people to adopt good LLIN maintainance practices.

Enhanced phytase production by Aspergillus niger mutants in solid state fermentation

The present research work was conducted to improve the phytase production by genetic alteration of Aspergillus niger with induced mutagenesis using solid state fermentation. Strain improvement was carried out in the presence of ultra violet (UV) irradiation and ethylmethane sulphonate (EMS) [0.5% v/v] treatments for various time intervals. We reported an improved strain of Aspergillus niger designated as UV-3 mutant producing a zone of hydrolysis of about 40 mm, in comparison to wild strain (26 mm). The highest enzyme activity was found to be 547.64 IU/g for UV-3 mutant followed by EMS-4 mutant (492.23 IU/g)compared to wild strain which showed 406.45 IU/g of enzyme activity. There was 1.35 fold increase in phytase production after mutation studies of Aspergillus niger. Phytase was applied as poultry feed additive and given to broiler chickens for 5 weeks. The results exhibited that there was increase in body weight gain (BWG) of chicks for experimental group (2028 g) in comparison to control group (1903 g). Thus, physical and chemical mutagenesis was proved as an effective technique for the improvement of strain and ultimately for enhanced and economical phytase production for different industrial applications.

Characterization of the Biosynthetic Gene Cluster of Enterocin F4-9, a Glycosylated Bacteriocin

Enterocin F4-9 belongs to the glycocin family having post-translational modifications by two molecules of N-acetylglucosamine β-O-linked to Ser37 and Thr46. In this study, the biosynthetic gene cluster of enterocin F4-9 was cloned and expressed in Enterococcus faecalis JH2-2. Production of glycocin by the JH2-2 expression strain was confirmed by expression of the five genes. The molecular weight was greater than glycocin secreted by the wild strain, E. faecalis F4-9, because eight amino acids from the N-terminal leader sequence remained attached. This N-terminal extension was eliminated after treatment with the culture supernatant of strain F4-9, implying an extracellular protease from E. faecalis F4-9 cleaves the N-terminal sequence. Thus, leader sequences cleavage requires two steps: the first via the EnfT protease domain and the second via extracellular proteases. Interestingly, the long peptide, with N-terminal extension, demonstrated advanced antimicrobial activity against Gram-positive and Gram-negative bacteria. Furthermore, enfC was responsible for glycosylation, a necessary step prior to secretion and cleavage of the leader peptide. In addition, enfI was found to grant self-immunity to producer cells against enterocin F4-9. This report demonstrates specifications of the minimal gene set responsible for production of enterocin F4-9, as well as a new biosynthetic mechanism of glycocins.