Assessment of bioflocculant production by some marine bacteria isolated from the bottom sediment of Algoa Bay

Several problems concerning the use of conventional synthetic flocculants has necessitated the need for alternative cost effective, safe and efficient bioflocculants from microorganisms inhabiting many environments, particularly those from unusual environments. Hence, this study assessed bioflocculant production by three marine bacteria isolated from the bottom sediment of Algoa Bay in the Eastern Cape Province of South Africa. Analysis of the 16S rDNA sequences led to their identification as Halobacillus sp. Mvuyo, Virgibacillus sp. Rob and Oceanobacillus sp. Pinky. Several factors affecting the production and activity of the bioflocculant(s) were studied. Halobacillus sp. Mvuyo produced bioflocculant optimally with glucose (76%) and ammonium chloride (93%) as sole carbon and nitrogen sources, respectively and at neutral pH and in the presence of Ca2+. On the other hand, Virgibacillus sp. Rob preferred glucose (70.4 %) and iron sulphate (74%) as carbon and nitrogen source respectively; an alkaline pH (12.0) and Fe2+. Oceanobacillus sp. Pinky produced bioflocculant optimally when sucrose (80%) and peptone (72.4 %) were used as carbon and nitrogen source respectively, at neutral pH, and in the presence of Ca2+ cation. The chemical analyses of the partially purified bioflocculants revealed that the bioflocculants produced by Halobacillus sp. Mvuyo and Oceanobacillus sp. Pinky were glycoproteins, while that produced by Virgibacillus sp. Rob was a polysaccharide. We thus conclude that Halobacillus sp. Mvuyo, Virgibacillus sp. Rob and Oceanobacillus sp. Pinky hold promise as producers of new and efficient bioflocculant(s). We recommended development of process conditions for large scale production of the bioflocculants followed by their detailed characterization, as well as pilot scale assessment of the applicability of the purified bioflocculant in water/wastewater treatment and other industrial use

An andrographolide from helichrysum caespitium (DC.) sond. Ex Harv., (Asteraceae) and Its antimicrobial, antiquorum sensing, and antibiofilm potentials

Helichrysum caespititium (DC.) Sond. Ex Harv., (Asteraceae) is a medicinal plant indigenous to South Africa. Its non-polar extracts exhibit significant antimicrobial and, in particular, antigonorrheal activity. This study aimed at isolating and purifying the active antigonorrheal compound from its chloroform extract and validating its inhibition potential on quorum sensing (QS) and biofilm formation of multi-drug resistant (MDR) pathogens. Phytochemical investigation of aerial parts of H. caespititium afforded a diterpene lactone (CF6). The effect of CF6 on violacein production and biofilm formation was studied using in vitro quantitative violacein inhibition (Chromobacterium violaceum) and biofilm formation (Streptococcus pyogenes, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Neisseria gonorrhoeae, and Pseudomonas aeruginosa). The structure of CF6 was characterized using FTIR, NMR, and UPLC-MS data accordingly, as 10-methyl-8-(propan-17-ylidene)naphthalen-9-yl)-11-vinyl- 14-hydroxyfuran-16-one. The susceptibility testing of the pathogens against CF6 revealed Neisseria gonorrhoeae was noticeably susceptible with a MIC value of 60 g/mL, while Streptococcus pyogenes and Staphylococcus aureus showed MIC of 125 g/mL. All gram-negative pathogens, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa were inhibited at 250 g/mL. CF6 also inhibited the production of violacein by 51.88% at 250 g/mL and prevented cell attachment by 40.76–81.18%, with N. gonorrhoeae being highly prohibited from forming biofilm. In conclusion, 10-methyl-8-(propan-17- ylidene)naphthalen-9-yl)-11-vinyl-14-hydroxyfuran-16-one is the first of its kind to be isolated from the non-polar (chloroform) extract of South African Helichrysum caespititium with antigonorrheal, antimicrobial, antiquorum sensing, and antibiofilm properties. The compound may serve as a drug candidate against MDR pathogens.SUPPLEMENTARY MATERIAL : FIGURE S1: The proton (1H NMR) spectrum of CF6. FIGURE S2: The carbon-13 (13CNMR) spectrum of CF6. FIGURE S3: Correlation spectroscopy (COSY) spectrum of CF6. FIGURE S4: Attached proton test (ATP) spectrum of CF6. FIGURE S5: Heteronuclear Single Quantum Coherence (HSQC) spectrum of CF6. FIGURE S6: Heteronuclear multiple bond correlation (HMBC) spectrum of CF6 and FIGURE S7: High resolution electrospray ionization mass spectrometry (HRESIMS) spectrum of CF6.The South African National Research Foundation (NRF) Thuthuka Grant, South African Medical Research Council–Self Initiated Research (SAMRC-SIR), and Sefako Makgatho Health Sciences University Research and Development Grant.https://www.mdpi.com/journal/biologyam2022BiochemistryGeneticsMicrobiology and Plant Patholog

Anti-biofilm and associated anti-virulence activities of selected phytochemical compounds against Klebsiella pneumoniae

The ability of Klebsiella pneumoniae to form biofilm renders the pathogen recalcitrant to various antibiotics. The difficulty in managing K. pneumoniae related chronic infections is due to its biofilm-forming ability and associated virulence factors, necessitating the development of efficient strategies to control virulence factors. This study aimed at evaluating the inhibitory potential of selected phytochemical compounds on biofilm-associated virulence factors in K. pneumoniae, as well as authenticating their antibiofilm activity. Five phytochemical compounds (alpha-terpinene, camphene, fisetin, glycitein and phytol) were evaluated for their antibacterial and anti-biofilmassociated virulence factors such as exopolysaccharides, curli fibers, and hypermucoviscosity against carbapenem-resistant and extended-spectrum beta-lactamase-positive K. pneumoniae strains. The antibiofilm potential of these compounds was evaluated at initial cell attachment, microcolony formation and mature biofilm formation, then validated by in situ visualization using scanning electron microscopy (SEM). Exopolysaccharide surface topography was characterized using atomic force microscopy (AFM). The antibacterial activity of the compounds confirmed fisetin as the best anti-carbapenem-resistant K. pneumoniae, demonstrating a minimum inhibitory concentration (MIC) value of 0.0625 mg/mL. Phytol, glycitein and α-terpinene showed MIC values of 0.125 mg/mL for both strains. The assessment of the compounds for anti-virulence activity (exopolysaccharide reduction) revealed an up to 65.91% reduction in phytol and camphene. Atomic force microscopy detected marked differences between the topographies of untreated and treated (camphene and phytol) exopolysaccharides. Curli expression was inhibited at both 0.5 and 1.0 mg/mL by phytol, glycitein, fisetin and quercetin. The hypermucoviscosity was reduced by phytol, glycitein, and fisetin to the shortest mucoid string (1 mm) at 1 mg/mL. Phytol showed the highest antiadhesion activity against carbapenem-resistant and extended-spectrum beta-lactamase-positive K. pneumoniae (54.71% and 50.05%), respectively. Scanning electron microscopy correlated the in vitro findings, with phytol significantly altering the biofilm architecture. Phytol has antibiofilm and antivirulence potential against the highly virulent K. pneumoniae strains, revealing it as a potential lead compound for the management of K. pneumoniae-associated infections.Supplementary Materials: Table S1: Exopolysaccharide reduction in K. pneumoniae (ATCC 700603 and ATCC BAA-1705) by studied phytochemical compounds.The South African Medical Research Council—Self-Initiated Research (SAMRC-SIR) and partly by the South African National Research Foundation (NRF) Thuthuka Grant.https://www.mdpi.com/journal/plantsdm2022Biochemistr

Quorum sensing modulation and inhibition in biofilm forming foot ulcer pathogens by selected medicinal plants

The crisis of antibiotic resistance necessitates the search of phytochemicals as potential antibacterial, anti-quorum sensing and antibiofilm forming agents. For the present study, fifteen (15) selected medicinal plants were evaluated to inhibit the biological activities of multi-drug resistant (MDR) pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis) associated with diabetic foot ulcer. Antibacterial activities revealed noteworthy minimum inhibitory concentration (MIC) values ≤1 mg/mL for thirteen (13) out of the sixty (60) plant extracts screened. The potent extracts included Euclea natalensis ethyl acetate (0.25 mg/mL), Aloe ferox methanol (0.5 mg/ml) and Warburgia salutaris aqueous (0.5 mg/mL) extracts. Chemical profiling of the active extracts using gas chromatography-mass spectrometry (GC-MS) identified neophytadiene, guanosine, squalene, cis megastigma-5,8-diene-4-one and sorbitol as prevalent compounds among the active extracts. Anti-quorum sensing activities of E. natalensis (ethyl acetate), A. ferox (methanol) and W. salutaris (aqueous) extracts ranged from 4.81 - 58.34% with E. natalensis (ethyl-acetate) showing the highest activity. Molecular docking against CviR protein showed selected compounds having high docking scores with sorbitol showing the highest score of -7.04 kcal/mol. Warburgia salutaris aqueous extract exhibited the highest biofilm inhibition (73%) against E. coli. Euclea natalensis, Aloe ferox and Warburgia salutaris compounds act as antagonist of N-acyl homoserine lactone (AHL) signaling, thus may serve as candidates in antipathogenic and antibiofilm phytomedicine development for MDR foot ulcer bacterial pathogens.The South African National Research Foundation (NRF) Thuthuka Grant and the South African Medical Research Council-Self Initiated Research (SAMRC-SIR).https://www.cell.com/heliyon/homeBiochemistryGeneticsMicrobiology and Plant PathologyPlant Production and Soil Scienc

Assessment of Bioflocculant Production by Bacillus sp. Gilbert, a Marine Bacterium Isolated from the Bottom Sediment of Algoa Bay

The bioflocculant-producing potentials of a marine bacteria isolated from the bottom sediment of Algoa Bay was investigated using standard methods. The 16S rDNA sequence analysis revealed 98% similarity to that of Bacillus sp. HXG-C1 and the nucleotide sequence was deposited in GenBank as Bacillus sp. Gilbert with accession number HQ537128. Bioflocculant was optimally produced when sucrose (72% flocculating activity) and ammonium chloride (91% flocculating activity) were used as sole sources of carbon and nitrogen, respectively; an initial pH 6.2 of the production medium; and Mg2+ as cation. Chemical analysis of the purified bioflocculant revealed the compound to be a polysaccharide

Studies on Bioflocculant Production by Arthrobacter sp. Raats, a Freshwater Bacteria Isolated from Tyume River, South Africa

A bioflocculant-producing bacteria was isolated from Tyume River in the Eastern Cape Province, South Africa and identified by 16S rRNA gene nucleotide sequence to have 91% similarity to Arthrobacter sp. 5J12A, and the nucleotide sequence was deposited in GenBank as Arthrobacter sp. Raats (accession number HQ875723). The bacteria produced an extracellular bioflocculant when grown aerobically in a production medium containing glucose as sole carbon source and had an initial pH of 7.0. Influences of carbon, nitrogen and metal ions sources, as well as initial pH on flocculating activity were investigated. The bacteria optimally produced the bioflocullant when lactose and urea were used as sole sources of carbon and nitrogen respectively with flocculating activities of 75.4% and 83.4% respectively. Also, the bacteria produced the bioflocculant optimally when initial pH of the medium was 7.0 (flocculating activity 84%), and when Mg2+ was used as cation (flocculating activity 77%). Composition analyses indicated the bioflocculant to be principally a glycoprotein made up of about 56% protein and 25% total carbohydrate

Antiuropathogenic and antioxidant activities of Hypoxis hemerocallidea Lam. extracts, and compounds from its taxonomically related species

Hypoxis hemerocallidea Lam is one of the 43 Hypoxis species in South Africa, marketed extensively as over the counter herbal product for the management of several diseases. The plant commercial products link efficacy to hypoxoside 4, its aglycone (rooperol), or β-sitosterol. This study investigated antibacterial and anti-oxidant activities of four other molecules and two extracts from the Hypoxis plant. Visual antioxidant limit of detection and free radical scavenging activities of test samples were determined using 20 mM hydrogen peroxide, 0.4 mM DPPH or ferric reducing antioxidant power assay. Quantitative free radical was determine by spectrophotometric method while antibacterial activity was evaluated using MICs against uropathogens: S. aureus (ATCC25923), S. marcescens (ATCC 14041), P. aeruginosa (ATCC 9721), P. mirabilis (ATCC 33583) and E. coli (ATCC 10536). Anti-oxidant activities visual limit of detection of 0.06 mg/mL and percentage free radical scavenging activity (IC50 = 0.048 - 0.032 mg/ml) for pure compounds 1 - 4 and (IC50 = 0.037 - 0.039 mg/ml) for extracts were obtained. The reducing power IC50 ranged between 0.15 - 0.23 mg/ml for extracts and 0.11-0.35 mg/ml for standards. Antibacterial potentials show a noteworthy to moderate MIC values of 0.20 - 1.56 mg/ml against S. aureus (ATCC 25923), S. marcescens (ATCC 14041), P. aeruginosa (ATCC 9721), P. mirabilis (ATCC 33583) and E. coli (ATCC 10536). Galpinoside 5, hemerocalloside 3 and curculigoside C 2 are the other active compounds in Hypoxis plant