Evaluation of antagonistic actinomycetes isolates as biocontrol agents against wastewater-associated bacteria

Characterization and evaluation of actinomycete from the Protaetia brevitarsis Larva Frass

Protaetia brevitarsis larvae (PBL) are soil insects important for the soil organic carbon cycle, and PBL frass not only contains a large amount of humic acid but also affects the diversity, novelty, and potential functions of actinomycetes. Here, we characterized and assessed the actinomycete. The operational taxonomic unit (OTU) data showed that 90% of the actinomycetes cannot be annotated to species, and pure culture and genome analysis showed that 35% of the strains had the potential to be new species, indicating the novelty of PBL frass actinomycetes. Additionally, genome annotation showed that many gene clusters related to antifungal, antibacterial and insecticidal compound synthesis were identified, and confrontation culture confirmed the antifungal activities of the actinomycetes against soil-borne plant pathogenic fungi. The incubation experiment results showed that all isolates were able to thrive on media composed of straw powder and alkaline lignin. These results indicated that PBL hindgut-enriched actinomycetes could survive in soil by using the residual lignocellulose organic matter from plant residues, and the antibiotics produced not only give them a competitive advantage among soil microflora but also have a certain inhibitory effect on plant diseases and pests. This study suggests that the application of PBL frass can not only supplement soil humic acid but also potentially affect the soil microbiota of cultivated land, which is beneficial for the healthy growth of crops.

Efficacy of simultaneous advanced oxidation and adsorption for treating municipal wastewater for indirect potable reuse

The main scope of this study was to compare the efficacy of different advanced oxidation processes (AOPs) combined with adsorption for treating secondary treated effluent of municipal wastewater in a continuous-lab-scale reactor. The results revealed enhanced removal of biological oxygen demand (BOD: C₀: 14.1 and C_t: 0 mg L^-1 (100%)), chemical oxygen demand (COD: C₀: 40.5 and C_t: 4 mg L^-1 (≤90%)), and total organic carbon (TOC: C₀: 15.2 and C_t: 3.02-3.63 mg L^-1 (∼80%)) by UV/PMS, O₃/PMS, UV/O₃/H₂O₂, and UV/O₃/MnO₂ processes followed by glass packed bed reactor (GPBR). Complete inactivation of the bacterial count was observed for all the studied processes. The GPBR showed the additional advantage of termination in the regrowth of bacterial count on the filtering medium. The gas-chromatography and mass spectrometry (GC-MS) analysis showed that AOP followed by adsorption reduced the concentrations of the by-products in the treated effluent. Overall, the synergy between AOP and adsorption improved the effluent quality to meet various indirect potable reuse (IPR) applications.

Unravelling the genetic potential for hydrocarbon degradation in the sediment microbiome of Antarctic islands

Hydrocarbons may have a natural or anthropogenic origin and serve as a source of carbon and energy for microorganisms in Antarctic soils. Herein, 16S rRNA gene and shotgun sequencing were employed to characterize taxonomic diversity and genetic potential for hydrocarbon degradation of the microbiome from sediments of sites located in two Antarctic islands subjected to different temperatures, geochemical compositions, and levels of presumed anthropogenic impact, named: Crater Lake/Deception Island (pristine area), Whalers Bay and Fumarole Bay/Deception Island (anthropogenic-impacted area), and Hannah Point/Livingston Island (anthropogenic-impacted area). Hydrocarbon concentrations were measured for further correlation analyses with biological data. The majority of the hydrocarbon-degrading genes were affiliated to the most abundant bacterial groups of the microbiome: Proteobacteria and Actinobacteria. KEGG annotation revealed 125 catabolic genes related to aromatic hydrocarbon (styrene, toluene, ethylbenzene, xylene, naphthalene, and polycyclic hydrocarbons) and aliphatic (alkanes and cycloalkanes) pathways. Only aliphatic hydrocarbons, in low concentrations, were detected in all areas, thus not characterizing the areas under study as anthropogenically impacted or nonimpacted. The high richness and abundance of hydrocarbon-degrading genes suggest that the genetic potential of the microbiome from Antarctic sediments for hydrocarbon degradation is driven by natural hydrocarbon occurrence.

Study of the Antimicrobial Potential of Actinomycetes Isolated from Organic and Inorganic Waste

The main objective of this investigation was to characterize a collection of actinomycetes strains isolated from unexplored polluted ecosystems and to evaluate their antimicrobial potential in order to discover interesting bioactive compounds. Based on morphological and culture characters, 32 different strains were isolated: 20 strains from compost heap, seven strains from manure, and five strains from waste water. As expected, the genus Streptomyces was the most prevalent followed by the genus Micromonospora. Analysis of the antimicrobial activities of the isolated strains showed that those from compost heap were more efficient against the tested microorganisms (Candida albicans, Methicillin-resistant Staphylococcus aureus, Staphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli). Several bioactive compounds were identified by liquid chromatography (LC) combined with mass spectrometry (MS) and then analyzed by both MEDINA's database, which contains the most common secondary metabolites, and Dictionary of Natural Products Chapman & Hall. Many interesting well-known and unknown biomolecules were identified. Quinomycin A and Daidzein were the most fascinating compounds isolated, respectively, by Streptomyces sp. WW2 and Streptomyces sp. WW4. The most active strain was identified based on 16S rDNA's sequences and it seems to be a new strain. The crude extract of the strain CH12 was analyzed and the UV absorption spectra and mass spectra (MS) of the main active compound were reported. It's an interesting compound (possible purpuromycin) with the molecular formula C26H18O13.

Co-culture of microalga Chlorella sorokiniana with syntrophic Streptomyces thermocarboxydus in cassava wastewater for wastewater treatment and biodiesel production

This study aimed to conduct a co-culture of a microalga and syntrophic actinomycetes to treat cassava a biogas effluent wastewater and enhance biodiesel production. Streptomyces thermocarboxydus strain BMI 10 produced the greatest effect on biomass production by Chlorella sorokiniana strain P21. Maximal algal biomass production and total lipid yield were increased when strain BMI 10 was co-cultured (by 21 and 25 %, respectively). Furthermore, the nutrient removal efficiency of P21 was not significantly different under sterilized and unsterilized conditions. Harvestability of the strain was also increased under both conditions. Analysis of the amount and composition of fatty acids from this co-culture biomass revealed that it was quite satisfactory for biodiesel production (54.11-61.52% saturated fatty acids with a 0.59-0.82 degree of unsaturation). Overall, the results showed the co-culture of the alga and bacterium is a holistic enhancement that couples wastewater treatment with biodiesel production.

Isolation, Identification, Biocontrol Activity, and Plant Growth Promoting Capability of a Superior Streptomyces tricolor Strain HM10

Streptomyces is a genus with known biocontrol activity, producing a broad range of biologically active substances. Our goal was to isolate local Streptomyces species, evaluate their capacity to biocontrol the selected phytopathogens, and promote the plant growth via siderophore and indole acetic acid (IAA) production and phosphate solubilization. Eleven isolates were obtained from local soil samples in Saudi Arabia via the standard serial dilution method and identified morphologically by scanning electron microscope (SEM) and 16S rRNA amplicon sequencing. The biocontrol of phytopathogens was screened against known soil-borne fungi and bacteria. Plant growth promotion capacity was evaluated based on siderophore and IAA production and phosphate solubilization capacity. From eleven isolates obtained, one showed 99.77% homology with the type strain Streptomyces tricolor AS 4.1867, and was designated S. tricolor strain HM10. It showed aerial hyphae in SEM, growth inhibition of ten known phytopathogens in in vitro experiments, and the production of plant growth promoting compounds such as siderophores, IAA, and phosphate solubilization capacity. S. tricolor strain HM10 exhibited high antagonism against the fungi tested (i.e., Colletotrichum gloeosporides with an inhibition zone exceeding 18 mm), whereas the lowest antagonistic effect was against Alternaria solani (an inhibition zone equal to 8 mm). Furthermore, the most efficient siderophore production was recorded to strain HM8, followed by strain HM10 with 64 and 22.56 h/c (halo zone area/colony area), respectively. Concerning IAA production, Streptomyces strain HM10 was the most effective producer with a value of 273.02 μg/ml. An autochthonous strain S. tricolor HM10 should be an important biological agent to control phytopathogens and promote plant growth.

Plasmid profiles and antibiotic susceptibility patterns of bacteria isolated from abattoirs wastewater within Ilorin, Kwara, Nigeria

Background and Objectives:

Waste water from abattoirs could harbour bacteria some of which are pathogenic. Therefore, this study aimed to assess the quality of wastewater from some abattoirs in Ilorin, Nigeria.

Materials and Methods:

The counts of viable bacteria, total coliform, faecal coliform, enterococci, S. aureus, P. aeruginosa and Salmonella/Shigella spp. of the wastewater was determined using selective media. The sanitary condition appraisal, antibiotic susceptibility test and plasmid profile of the isolates were assessed using standard methods.

Results:

The highest count of viable bacteria and total coliform obtained were 9.0 × 10⁷ and 3.0 × 10⁷ CFU/ml respectively. Faecal coliform and enterococcal count had the same highest value of 3.0 × 10⁵ CFU/ml. The highest count of pathogenic bacteria: Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella spp. were 2.5 × 10⁸, 1.9 × 10⁷ and 3.0 × 10⁴ CFU/ml respectively. The abattoirs sanitary scores ranged from 28.6–57.1%. The isolates showed multiple antibiotic resistance (MAR) index ranging from 0.5–1.0. Plasmid curing with 0.1 mg/ml of acridine orange solution led to reduction in the MAR index of most of the Gram negative bacteria. Pseudomonas stutzeri was susceptible to all the antibiotics while Proteus vulgaris was resistant to all the antibiotics after curing. Most of the Gram negative bacteria isolated belong to the families Enterobacteriaceae and Pseudomonadaceae while the Gram positive bacteria belong to the families Staphylococcaceae, Enterococcaceae and Streptococcaceae.

Conclusion:

It was concluded from this study that wastewaters from the abattoirs were contaminated by bacteria with high MAR index. Most of these bacteria borne their antibiotic resistant factors in their plasmid.