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Articles by Khayalethu Ntushelo
Total Records ( 4 ) for Khayalethu Ntushelo
  Sarah Otun and Khayalethu Ntushelo
  The infection process of Sclerotinia sclerotiorum (Lib.) de Bary, a necrotrophic plant pathogen with more than 600 host plants, causing several disease symptoms such as cottony rot, watery soft rot, stem rot, white mould etc in a wide range of host plants remains sketchy. Specifically, virulence factors produced during host invasion require a special compilation to provide various researchers with this critical knowledge. This review discussed the virulence factors produced by S. sclerotiorum during plant invasion and colonization. The discussion was organized under the topics of S. sclerotiorum necrotrophic lifestyle, weaponry and the molecular aspect of its pathogenicity, zooming-in on the roles of its virulence factors (Cell wall degrading enzymes, effectors and oxalic acid) during pathogenicity.
  Mvuyisi Mivuyo Surrender Mbovane and Khayalethu Ntushelo
  Background and Objective: Acetaldehyde is an inhibitor of growth of fungi including Alternaria alternata and alters biochemical processes. However, its effect on the regulation of the production of amino acids in A. alternata remained unknown. This study aimed to investigate the inhibition and co-regulation of five amino acids produced in Alternaria alternata exposed to acetaldehyde. Materials and Methods: To assess the regulation of the production of amino acids in A. alternata exposed to acetaldehyde colonies of this fungus were exposed this volatile compound at concentrations of 0, 5 and 10% over 24, 48, 96 and 120 h. Results: Results showed that acetaldehyde inhibited A. alternata mycelial growth in a dose-dependent manner. Moreover, evidence of suppression and co-regulation of the production of amino acids, leucine, isoleucine, proline, tyrosine and valine was discovered. Conclusion: From these results it could be concluded that acetaldehyde can suppress and co-regulate the production of the five amino acids.
  Khayalethu Ntushelo
  Background and Objective: Salicylic acid is a signal molecule which activates plant defense against plant pathogens such as the soft rot enterobacterium Pectobacterium carotovorum subsp. carotovorum. The objectives of study were to determine bactericidal effects of salicylic acid on the growth of P. carotovorum subsp. carotovorum and secondly, assess chemical responses of P. carotovorum subsp. carotovorum to salicylic acid. Materials and Methods: Pectobacterium carotovorum subsp. carotovorum was grown in lysogeny broth amended with salicylic acid at concentrations of 0, 100, 200, 400, 800 and 1200 mg L–1. The P. carotovorum subsp. carotovorum cultures were incubated at 25°C and sampled at two time points, 0 h (sampled before incubation) and 24 h. Bacterial counts were done at the onset of the incubation (0 h) and after the 24 h incubation. The set which was incubated for 24 h was split into two, one subset was centrifuged and the other was not. From the centrifuged subset the supernatant was recovered and was, together with all the other samples (0 and 24 h not centrifuged), analyzed with1H nuclear magnetic resonance and gas chromatography. Results: Bacterial counts done before and after incubation showed that the lower concentrations of salicylic acid, 0, 100, 200 and 400 mg L–1, supported the growth of P. carotovorum subsp. carotovorum whereas the higher concentrations of 800 and 1200 mg L–1 inhibited the growth of the bacterium completely. Nuclear magnetic resonance results showed either slight or no differences in the metabolite profiles and gas chromatography showed different responses without a clearly defined pattern among the experimental treatments. However, methanethiol was detected by both nuclear magnetic resonance and gas chromatography in all the treatments and was probably formed as a result of the breakdown of lysogeny broth. Conclusion: From the results obtained it was concluded that salicylic acid promotes the growth of P. carotovorum subsp. carotovorum at lower concentrations of 0-400 mg L–1 but higher concentrations of salicylic acid of 800 and 1200 mg L–1 inhibit bacterial growth. All the tested salicylic acid concentrations (0-1200 mg L–1) cause only slight chemical shifts in the bacterial culture. Methanethiol was detected in all treatments and it is probably formed from the breakdown of lysogeny broth.
  Venkata Subba Reddy Gangireddygari , DileepKumar Kanderi , Ramanjaneyulu Golla , Manjunatha Bangeppagari , Vijay Anand Kumar Babu Gundi , Khayalethu Ntushelo and Rajasekhar Reddy Bontha
  Background and Objective: A widely used pesticide quinalphos (O, O-diethyl O-quinoxalin-2-yl phosphorothioate) may be an undesirable and persistent pollutant to non-target environments like rivers and other ecosystems. The objective of this study was to isolate a potential degradant bacterium of quinalphos from polluted soils and test its fitness under various culture conditions. Materials and Methods: A soil bacterium strain, capable of utilizing quinalphos as its sole source of carbon and energy was isolated from soil by enrichment method on a minimal salts medium (MSM). On the basis of morphological, biochemical and 16S rRNA gene sequence analysis the bacterium is a species of the genus Bacillus and it was closely related to Bacillus subtilis. Quinalphos degrading capabilities of this bacterium were assessed under different culture conditions. Quinalphos degradation data were analysed byusing a two-way ANOVA analysis with the Statistica v.10. Results: Bacillus subtilis grew on quinalphos with a generation time of 32.34 min or 0.54 h in the logarithmic phase. Maximum degradation of quinalphos was observed with an inoculum of 1.0 optical density, around pH-7.5 and at an optimum temperature of 35-37°C. Among the additional carbon and nitrogen sources, carbon source-glucose and nitrogen source-yeast extract marginally improved the rate of degradation of quinalphos. Gas chromatography-mass spectrometry (GC-MS) analysis of the culture of B. subtilis grown on quinalphos indicated the formation of one main metabolite-quinoxaline. Conclusion: The B. subtilis strain discovered in this study has a unique combination of abilities to degrade quinalphos and it is therefore suitable candidate bioremediator of quinalphos polluted environments.
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