Characterization of polygalacturonases from fruit spoilage Fusarium oxysporum and Aspergillus tubingensis

We reported the partial purification and characterization of polygalacturonases from fruit spoilage Fusarium oxysporum and Aspergillus tubingensis isolated from banana and peach, respectively. By using diethylaminoethyl (DEAE)-Sepharose column, one and two forms of polygalacturonases were separated from F. oxysporum (PGase) and A. tubingensis (PGaseI and PGaseII), respectively. The polygalacturonases examined had higher affinity toward various polygalacturonic acids and pectins. The apparent Km and Vmax values were reported for the enzymes. Acidic pH optima (4.0 to 6.0) was also reported for the enzymes. Optimal temperature and thermal stability of the enzymes showed a range from 40 to 60°C. The effect of metal cations on the enzymes was studied. The most chemical compounds caused moderate inhibitory effect except benzoic and citric acids which had strong inhibitory effect on the polygalacturonases. The benzoic and citric acids were used as antifungal compounds for F. oxysporum and A. tubingensis. The citric acid was found to be more effective against fungal growth than benzoic acid.Keywords: Fruit, spoilage, Fusarium oxysporum, Aspergillus tubingensis, polygalacturonas

Production of Functional Fermented Milk Beverages Supplemented with Pomegranate Peel Extract and Probiotic Lactic Acid Bacteria

Fermented milk beverages supplemented with pomegranate peel extract and inoculated with Lactobacillus plantarum and Bifidobacterium longum subsp longum were produced. The antioxidant activity of fermented milk beverages supplemented with pomegranate peel 150 mg/L (FMPO 150) and 300 mg/L (FMPO 300) was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). In addition, the polyphenolic profile and sugars content were determined by HPLC analysis, and the volatile compounds were identified using GC-MS analysis. The effects of FMPO 150 and FMPO 300 (10 g/day) on the lipid profile and antioxidant/biochemical status of rats were also evaluated after 4 weeks of oral intake. Antioxidant activity of the fermented milk beverage FMPO 300 was higher than that of FMPO 150. GC-MS analysis of the volatile compounds revealed that diacetyl, acetoin, and acetaldehyde were the major constituents. FMPO 150 and FMPO 300 were efficient in reducing the LDL cholesterol and triacylglycerol and increased the HDL cholesterol in serum. Liver function biomarkers were not affected by the end of treatment (p<0.05). Also, the thiobarbituric acid-reactive substances (TBARS) were decreased, while the activity of antioxidant enzymes in the liver (GSH, CAT, SOD, and GPx) were increased. Hence, the combination of pomegranate peel extract and probiotic lactic acid bacteria in a fermented milk beverage provides not only probiotic benefits but also bioactive phenolic compounds that could be functional and possess therapeutic effects

Beyond the Risk of Biofilms: An Up-and-Coming Battleground of Bacterial Life and Potential Antibiofilm Agents

Microbial pathogens and their virulence factors like biofilms are one of the major factors which influence the disease process and its outcomes. Biofilms are a complex microbial network that is produced by bacteria on any devices and/or biotic surfaces to escape harsh environmental conditions and antimicrobial effects. Due to the natural protective nature of biofilms and the associated multidrug resistance issues, researchers evaluated several natural anti-biofilm agents, including bacteriophages and their derivatives, honey, plant extracts, and surfactants for better destruction of biofilm and planktonic cells. This review discusses some of these natural agents that are being put into practice to prevent biofilm formation. In addition, we highlight bacterial biofilm formation and the mechanism of resistance to antibiotics

Isolation, Molecular Characterization and Probiotic Potential of Lactic Acid Bacteria in Saudi Raw and Fermented Milk

Probiotic bacteria can confer health benefits to the human gastrointestinal tract. Lactic acid bacteria (LAB) are candidate probiotic bacteria that are widely distributed in nature and can be used in the food industry. The objective of this study is to isolate and characterize LAB present in raw and fermented milk in Saudi Arabia. Ninety-three suspected LAB were isolated from thirteen different types of raw and fermented milk from indigenous animals in Saudi Arabia. The identification of forty-six selected LAB strains and their genetic relatedness was performed based on 16S rDNA gene sequence comparisons. None of the strains exhibited resistance to clinically relevant antibiotics or had any undesirable hemolytic activity, but they differed in their other probiotic characteristics, that is, tolerance to acidic pH, resistance to bile, and antibacterial activity. In conclusion, the isolates Lactobacillus casei MSJ1, Lactobacillus casei Dwan5, Lactobacillus plantarum EyLan2, and Enterococcus faecium Gail-BawZir8 are most likely the best with probiotic potentials. We speculate that studying the synergistic effects of bacterial combinations might result in a more effective probiotic potential. We suspect that raw and fermented milk products from animals in Saudi Arabia, especially Laban made from camel milk, are rich in LAB and have promising probiotic potential

Isolation and Characterization of a Novel Lytic Phage, vB_PseuP-SA22, and Its Efficacy against Carbapenem-Resistant \u3ci\u3ePseudomonas aeruginosa\u3c/i\u3e

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a serious public health threat in multiple clinical settings. In this study, we detail the isolation of a lytic bacteriophage, vB_PseuPSA22, from wastewater using a clinical strain of CRPA. Transmission electron microscopy (TEM) analysis identified that the phage had a podovirus morphology, which agreed with the results of whole genome sequencing. BLASTn search allowed us to classify vB_PseuP-SA22 into the genus Bruynoghevirus. The genome of vB_PseuP-SA22 consisted of 45,458 bp of double-stranded DNA, with a GC content of 52.5%. Of all the open reading frames (ORFs), only 26 (44.8%) were predicted to encode certain functional proteins, whereas the remaining 32 (55.2%) ORFs were annotated as sequences coding functionally uncharacterized hypothetical proteins. The genome lacked genes coding for toxins or markers of lysogenic phages, including integrases, repressors, recombinases, or excisionases. The phage produced round, halo plaques with a diameter of 1.5 ± 2.5 mm on the bacterial lawn. The TEM revealed that vB_PseuP-SA22 has an icosahedral head of 57.5 ± 4.5 nm in length and a short, non-contractile tail (19.5 ± 1.4 nm). The phage showed a latent period of 30 min, a burst size of 300 PFU/infected cells, and a broad host range. vB_PseuP-SA22 was found to be stable between 4–60 oC for 1 h, while the viability of the virus was reduced at temperatures above 60 oC. The phage showed stability at pH levels between 5 and 11. vB_PauP-SA22 reduced the number of live bacteria in P. aeruginosa biofilm by almost five logs. The overall results indicated that the isolated phage could be a candidate to control CRPA infections. However, experimental in vivo studies are essential to ensure the safety and efficacy of vB_PauP-SA22 before its use in humans

Bacteriophage-Based Biosensors: A Platform for Detection of Foodborne Bacterial Pathogens from Food and Environment

Foodborne microorganisms are an important cause of human illness worldwide. Two-thirds of human foodborne diseases are caused by bacterial pathogens throughout the globe, especially in developing nations. Despite enormous developments in conventional foodborne pathogen detection methods, progress is limited by the assay complexity and a prolonged time-to-result. The specificity and sensitivity of assays for live pathogen detection may also depend on the nature of the samples being analyzed and the immunological or molecular reagents used. Bacteriophage-based biosensors offer several benefits, including specificity to their host organism, the detection of only live pathogens, and resistance to extreme environmental factors such as organic solvents, high temperatures, and a wide pH range. Phage-based biosensors are receiving increasing attention owing to their high degree of accuracy, specificity, and reduced assay times. These characteristics, coupled with their abundant supply, make phages a novel bio-recognition molecule in assay development, including biosensors for the detection of foodborne bacterial pathogens to ensure food safety. This review provides comprehensive information about the different types of phage-based biosensor platforms, such as magnetoelastic sensors, quartz crystal microbalance, and electrochemical and surface plasmon resonance for the detection of several foodborne bacterial pathogens from various representative food matrices and environmental samples

Fresh Produce as a Potential Vector and Reservoir for Human Bacterial Pathogens: Revealing the Ambiguity of Interaction and Transmission

The consumer demand for fresh produce (vegetables and fruits) has considerably increased since the 1980s for more nutritious foods and healthier life practices, particularly in developed countries. Currently, several foodborne outbreaks have been linked to fresh produce. The global rise in fresh produce associated with human infections may be due to the use of wastewater or any contaminated water for the cultivation of fruits and vegetables, the firm attachment of the foodborne pathogens on the plant surface, and the internalization of these agents deep inside the tissue of the plant, poor disinfection practices and human consumption of raw fresh produce. Several investigations have been established related to the human microbial pathogens (HMPs) interaction, their internalization, and survival on/within plant tissue. Previous studies have displayed that HMPs are comprised of several cellular constituents to attach and adapt to the plant’s intracellular niches. In addition, there are several plant-associated factors, such as surface morphology, nutrient content, and plant–HMP interactions, that determine the internalization and subsequent transmission to humans. Based on documented findings, the internalized HMPs are not susceptible to sanitation or decontaminants applied on the surface of the fresh produce. Therefore, the contamination of fresh produce by HMPs could pose significant food safety hazards. This review provides a comprehensive overview of the interaction between fresh produce and HMPs and reveals the ambiguity of interaction and transmission of the agents to humans

The Battle between Bacteria and Bacteriophages: A Conundrum to Their Immune System

Bacteria and their predators, bacteriophages, or phages are continuously engaged in an arms race for their survival using various defense strategies. Several studies indicated that the bacterial immune arsenal towards phage is quite diverse and uses different components of the host machinery. Most studied antiphage systems are associated with phages, whose genomic matter is double-stranded-DNA. These defense mechanisms are mainly related to either the host or phage-derived proteins and other associated structures and biomolecules. Some of these strategies include DNA restriction-modification (R-M), spontaneous mutations, blocking of phage receptors, production of competitive inhibitors and extracellular matrix which prevent the entry of phage DNA into the host cytoplasm, assembly interference, abortive infection, toxin–antitoxin systems, bacterial retrons, and secondary metabolite-based replication interference. On the contrary, phages develop anti-phage resistance defense mechanisms in consortium with each of these bacterial phage resistance strategies with small fitness cost. These mechanisms allow phages to undergo their replication safely inside their bacterial host’s cytoplasm and be able to produce viable, competent, and immunologically endured progeny virions for the next generation. In this review, we highlight the major bacterial defense systems developed against their predators and some of the phage counterstrategies and suggest potential research directions