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5. Biofilms on urban aquatic plastic pollution as a reservoir for pathogenic yeasts.

Author

Baker, Tyla, Bester, Armand, Sebolai, Olihile, Albertyn, Jacobus, and Pohl, Carolina

Subjects
WATER pollution, HUMAN ecology, FUNGAL communities, BACTERIAL diversity, YEAST
Abstract

Pollution of aquatic environments is a concern and poses a health risk to aquatic and terrestrial life. Plastic pollutants act as surfaces to which microorganisms adhere, forming a community known as the plastisphere. Studies investigating the bacterial diversity of the plastisphere are plentiful, but less is known about the fungal communities, especially yeasts, within these biofilms. Given the increasingly recognised threat of yeast infections, it is important to investigate the environmental presence of potential pathogenic yeasts on possible vehicles that may contribute to their distribution. In this study, the fungal diversity of the plastisphere of various types of plastic polymers collected from an urban freshwater source was analysed, and possibly pathogenic yeast strains were identified. Isolates were also tested for susceptibility to the antifungal, fluconazole. Microscopy sheds light on the overall diversity found in the plastisphere, while metagenomic data revealed that fungal plastisphere communities are dominated by the phylum Ascomycota. Both metagenomic and culture-dependant analysis revealed the presence of possibly pathogenic yeast in the genera Candida (some with low fluconazole susceptibility) and Exophiala. This highlights the possibility that the plastisphere may harbour pathogenic yeasts and could contribute to their distribution in the environment and transmission between the environment and humans. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Transcriptome Analyses of Candida albicans Biofilms, Exposed to Arachidonic Acid and Fluconazole, Indicates Potential Drug Targets

Author

Kuloyo, Oluwasegun, Fourie, Ruan, Cason, Errol, Albertyn, Jacobus, and Pohl, Carolina H.

Subjects
Antifungal Agents, Microbial Sensitivity Tests, c. albicans, Investigations, Biology, QH426-470, biofilm, Microbiology, Transcriptome, 03 medical and health sciences, chemistry.chemical_compound, Drug Resistance, Fungal, Candida albicans, fluconazole, medicine, arachidonic acid, Genetics, Humans, Molecular Biology, Beta oxidation, Genetics (clinical), 030304 developmental biology, chemistry.chemical_classification, 0303 health sciences, 030306 microbiology, Gene Expression Profiling, biology.organism_classification, Yeast, Corpus albicans, Pharmaceutical Preparations, chemistry, Biofilms, Arachidonic acid, Fluconazole, Polyunsaturated fatty acid, medicine.drug
Abstract

Candida albicans is an opportunistic yeast pathogen within the human microbiota with significant medical importance because of its pathogenic potential. The yeast produces highly resistant biofilms, which are crucial for maintaining infections. Though antifungals are available, their effectiveness is dwindling due to resistance. Alternate options that comprise the combination of existing azoles and polyunsaturated fatty acids, such as arachidonic acid (AA), have been shown to increase azoles susceptibility of C. albicans biofilms; however, the mechanisms are still unknown. Therefore, transcriptome analysis was conducted on biofilms exposed to sub-inhibitory concentrations of AA alone, fluconazole alone, and AA combined with fluconazole to understand the possible mechanism involved with the phenomenon. Protein ANalysis THrough Evolutionary Relationships (PANTHER) analysis from the differentially expressed genes revealed that the combination of AA and fluconazole influences biological processes associated with essential processes including methionine synthesis and those involved in ATP generation, such as AMP biosynthesis, fumarate metabolism and fatty acid oxidation. These observations suggests that the interference of AA with these processes may be a possible mechanisms to induce increased antifungal susceptibility.

Published
2020
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27. Role of the high-affinity reductive iron acquisition pathway of Candida albicans in prostaglandin E2 production, virulence, and interaction with Pseudomonas aeruginosa.

Author

Mochochoko, Bonang M, Ezeokoli, Obinna T, Sebolai, Olihile, Albertyn, Jacobus, and Pohl, Carolina H

Abstract

Components of the iron reductive pathway of Candida albicans have been implicated in the production of prostaglandin E2 (PGE2) and virulence. However, it is unknown whether other components of this pathway influence PGE2. We investigated the role of the iron reductive pathway of C. albicans in biofilm formation, PGE2 production, and virulence in Caenorhabditis elegans. Additionally, as the co-occurrence of C. albicans and Pseudomonas aeruginosa in host tissues is frequent and involves competition for host-associated iron, we examined the effects of this interaction. Deletion of multicopper oxidase gene, FET99 , and iron permease genes, FTH1 and FTH2 , affected biofilm metabolic activity, and for the FTH2 mutant, also biofilm morphology. Deletion of CCC1 (vacuolar iron transporter) and CCC2 (P-type ATPase copper importer) also influenced biofilm morphology. For PGE2 production, deletion of FET99, FTH1, FTH2, CCC1 , and CCC2 caused a significant reduction by monomicrobial biofilms, while FTH2deletion caused the highest reduction in polymicrobial biofilms. URA3 positive mutants of FET99 and FTH2 demonstrated attenuated virulence in C. elegans , potentially due to the inability of mutants to form hyphae in vivo. Deductively, the role of the iron reductive pathway in PGE2 synthesis is indirect, possibly due to their role in iron homeostasis. Lay Summary Iron uptake is vital for disease-causing microbes like Candida albicans. Using strains deficient in some iron-uptake genes, we show that iron-uptake genes, especially FET99 and FTH2 , play a role in biofilm formation, prostaglandin production, and virulence in the nematode infection model. [ABSTRACT FROM AUTHOR]

Published
2021
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28. Arachidonic acid metabolites in pathogenic yeasts

Author

Ells Ruan, Kock Johan LF, Albertyn Jacobus, and Pohl Carolina H

Subjects
Arachidonic acid, Oxylipins, Pathogenic, Yeasts, Nutritional diseases. Deficiency diseases, RC620-627
Abstract

Abstract Although most of what is known about the biology and function of arachidonic acid metabolites comes from the study of mammalian biology, these compounds can also be produced by lower eukaryotes, including yeasts and other fungi. It is also in this group of organisms that the least is known about the metabolic pathways leading to the production of these compounds as well as the functions of these compounds in the biology of fungi and yeasts. This review will deal with the discovery of oxylipins from polyunsaturated fatty acids, and more specifically the arachidonic acid derived eicosanoids, such as 3-hydroxy eicosatetraenoic acid, prostaglandin F2α and prostaglandin E2, in yeasts starting in the early 1990s. This review will also focus on what is known about the metabolic pathways and/or proteins involved in the production of these compounds in pathogenic yeasts. The possible roles of these compounds in the biology, including the pathology, of these organisms will be discussed.

Published
2012
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32. MAP kinase pathways in the yeast Saccharomyces cerevisiae

Author

Gustin, Michael C., Albertyn, Jacobus, Alexander, Matthew, and Davenport, Kenneth

Subjects
Cellular signal transduction -- Research, Protein kinases -- Physiological aspects, Saccharomyces -- Research, Biological sciences
Abstract

The five mitogen-activated protein kinase (MAPK) pathways observed in the yeast, Saccharomyces cerevisiae, were discussed. These pathways were the mating-pheromone response (MPR), cell integrity, filamentation-invasion, spore wall assembly and the high-osmolarity growth pathways. In the MPR pathway, Gbeta activation of the MPR cascade was influenced by downstream proteins, Ste5p and Ste20p. The MAPK cascade was necessary in signal transmission from the pheromone receptors in the plasma membranes to the nucleus. The pathway affected cell cycle arrest in reaction to pheromone.

Published
1998

36. Expression of rotavirus capsid protein, VP6, in various yeasts

Author

Rakaki, Matshepo Elizabeth, O’Neill, Hester G., Albertyn, Jacobus, Rakaki, Matshepo Elizabeth, O’Neill, Hester G., and Albertyn, Jacobus

Abstract

Rotavirus infection is one of the six leading causes of death among children under the age of five years. Globally it causes more than 215 000 deaths annually of which 65% occur in low- and/or middle-income countries. The two licenced live-attenuated vaccines (Rotarix™ and RotaTeq™) tend to have a lower efficacy in low- and/or middle-income countries. The lower efficacy of rotavirus live-attenuated vaccines could be due to maternal antibodies and oral polio vaccines interfering with rotavirus vaccine uptake. Rotavirus live-attenuated vaccines have been associated with reassortment with circulating genotype strains. As alternative, subunit vaccines such as viral proteins can be considered. Rotavirus VP6 protein is considered as a candidate for subunit vaccine development. Rotavirus VP6 antibodies are responsible for long lasting immunity and the antibodies against VP6 block the release of the viral mRNA. Previous studies showed rotavirus VP6 provide heterologous protection by a significant reduction of virus shedding in mice and gnotobiotic pigs. Various recombinant yeasts were engineered by a previous MSc student, Mr M.S. Makatsa, using a unique yeast expression vector (pKM177). The recombinant yeasts contained an open reading frame (ORF) encoding rotavirus VP6 for the RVA/Human wt/ZAF/GR10924/1999/G9P[6] strain. The ORF was codon optimised to favour expression in Arxula adeninivorans (AO), Kluyveromyces lactis (KO) and Pichia pastoris/Pichia angusta (PO). However, there was no expression of VP6 optimised for expression in A. adeninivorans and K. lactis due to an additional out-of-frame ATG in the promoter region of the expression vector. In this study, the additional ATG was successfully removed by site-directed mutagenesis and the Kozak sequence was optimised to produce modified delATG_pKM177_AOVP6 and delATG_pKM177_KOVP6 constructs. The modified delATG_pKM177_AOVP6, delATG_pKM177_KOVP6 as well as delATG_pKM177_POVP6, the modified plasmid containing the VP6 ORF co, National Research Foundation (NRF), PRF

Published
2018

39. Heterologous coexpression of the benzoate‐para‐hydroxylase CYP53B1 with different cytochrome P450 reductases in various yeasts.

Author

Theron, Chrispian W., Labuschagné, Michel, Albertyn, Jacobus, and Smit, Martha S.

Subjects
CYTOCHROME P-450, KLUYVEROMYCES marxianus, YEAST, REDUCTASES, ENZYMES, SACCHAROMYCES cerevisiae
Abstract

Summary: Cytochrome P450 monooxygenases (P450) are enzymes with high potential as biocatalysts for industrial applications. Their large‐scale applications are, however, limited by instability and requirement for coproteins and/or expensive cofactors. These problems are largely overcome when whole cells are used as biocatalysts. We previously screened various yeast species heterologously expressing self‐sufficient P450s for their potential as whole‐cell biocatalysts. Most P450s are, however, not self‐sufficient and consist of two or three protein component systems. Therefore, in the present study, we screened different yeast species for coexpression of P450 and P450‐reductase (CPR) partners, using CYP53B1 from Rhodotorula minuta as an exemplary P450. The abilities of three different coexpressed CPR partners to support P450 activity were investigated, two from basidiomycetous origin and one from an ascomycete. The various P450‐CPR combinations were cloned into strains of Saccharomyces cerevisiae, Kluyveromyces marxianus, Hansenula polymorpha, Yarrowia lipolytica and Arxula adeninivorans, using a broad‐range yeast expression vector. The results obtained supported the previous finding that recombinant A. adeninivorans strains perform excellently as whole‐cell biocatalysts. This study also demonstrated for the first time the P450 reductase activity of the CPRs from R. minuta and U. maydis. A very interesting observation was the variation in the supportive activity provided by the different reductase partners tested and demonstrated better P450 activity enhancement by a heterologous CPR compared to its natural partner CPR. This study highlights reductase selection as a critical variable for consideration in the pursuit of optimal P450‐based catalytic systems. The usefulness of A. adeninivorans as both a host for recombinant P450s and whole‐cell biocatalyst was emphasized, supporting earlier findings. [ABSTRACT FROM AUTHOR]

Published
2019
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41. Iron at the Centre of <italic>Candida albicans</italic> Interactions.

Author

Fourie, Ruan, Kuloyo, Oluwasegun O., Mochochoko, Bonang M., Albertyn, Jacobus, and Pohl, Carolina H.

Subjects
CANDIDA albicans, TOXICOLOGY of iron, PATHOGENIC microorganisms, GASTROINTESTINAL system, IRON bioavailability, CELL growth
Abstract

Iron is an absolute requirement for both the host and most pathogens alike and is needed for normal cellular growth. The acquisition of iron by biological systems is regulated to circumvent toxicity of iron overload, as well as the growth deficits imposed by iron deficiency. In addition, hosts, such as humans, need to limit the availability of iron to pathogens. However, opportunistic pathogens such as Candida albicans are able to adapt to extremes of iron availability, such as the iron replete environment of the gastrointestinal tract and iron deficiency during systemic infection. C. albicans has developed a complex and effective regulatory circuit for iron acquisition and storage to circumvent iron limitation within the human host. As C. albicans can form complex interactions with both commensal and pathogenic co-inhabitants, it can be speculated that iron may play an important role in these interactions. In this review, we highlight host iron regulation as well as regulation of iron homeostasis in C. albicans. In addition, the review argues for the need for further research into the role of iron in polymicrobial interactions. Lastly, the role of iron in treatment of C. albicans infection is discussed. [ABSTRACT FROM AUTHOR]

Published
2018
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43. Engineering yeast strains for the expression of South African G9P[6] rotavirus VP2 and VP6 structural proteins

Author

Makatsa, Mohau Steven, O’Neill, Hester G., Albertyn, Jacobus, Makatsa, Mohau Steven, O’Neill, Hester G., and Albertyn, Jacobus

Abstract

English: In this study, sequences encoding VP2 and VP6 rotavirus structural proteins from rotavirus strain RVA/Human-wt/ZAF/GR10924/1999/G9P[6] were used in construction of wide-range yeast expression vectors containing the ORFs encoding rotavirus structural proteins VP2 and VP6. VP2 and VP6 sequences were codon-optimized for expression in yeast strains K. lactis, A. adeninivorans and Pichia pastoris/Hansenula polymorpha. Wide-range yeast expression vectors containing either VP6 or VP2 yeast optimized ORFs were constructed for expression of single proteins in different yeast strains. Dual vectors containing both VP6 and VP2 yeast optimized ORFs were constructed to allow simultaneous expression of proteins in different yeast strains and to enable the formation of double-layered rotavirus-like particles. A total of eight yeast strains namely: Kluyveromyces marxianus, Kluyveromyces lactis, Debaryomyces hansenii, Yarrowia lipolytica, Hansenula polymorpha, Pichia pastoris Candida deformans and Arxula adeninivorans were selected for screening. Saccharomyces cerevisiae was included as a positive control as triple-layered rotavirus virus-like particles (tlRLPs) have been successfully produced in this yeast before. All nine yeast strains were successfully transformed with pKM177 vectors containing yeast codon-optimized VP6 ORFs. However, only six yeast strains indicated positive VP6 ORF integration. The other three yeast strains indicated no VP6 integration but hygromycin B integration suggesting that the vectors successfully integrated in these yeast strains but VP6 ORF was lost. Integration of both rotavirus VP2/6 ORFs was evident in all yeast strains transformed with the dual expression vectors. A control to monitor rotavirus VP6 protein expression in yeast was successfully prepared in bacterial cells. The positive control indicated specific reaction when polyclonal rotavirus antibody raised against Nebraska calf diarrhoea rotavirus strain. Rotavirus VP6 expression in yea, Afrikaans: In hierdie studie, basispaaropeenvolgings wat kodeer vir VP2 en VP6 rotavirus strukturele proteïene van rotavirus stam RVA/Human-wt/ZAF/GR10924/1999/G9P [6] is gebruik in die konstruksie van ‘n wye verskeidenheid gis uitdrukkingsvektore met rotavirus strukturele proteïene VP2 en VP6 oopleesrame. VP2 en VP6 basispaaropeenvolgings is kodon geoptimaliseer vir uitdrukking in gis stamme K. lactis, A. adeninivorans en P. pastoris/H. polymorpha. Wye verskeidenheid gis uitdrukkingsvektore wat geoptimaliseerde oopleesrame van VP6 of VP2 bevat, is gebou vir uitdrukking van enkel proteïene in verskillende gisstamme. Vektore wat beide VP6 en VP2 geoptimaliseerde oopleesrame bevat is gebou vir gelyktydige uitdrukking van proteïene in verskillende gisstamme en om die vorming van dubbellaag rotavirus-agtige partikels toe te laat. 'n Totaal van agt gisstamme naamlik: Kluyveromyces marxianus, Kluyveromyces lactis, Debaryomyces hansenii, Yarrowia lipolytica, Hansenula polymorpha, Pichia pastoris, Candida deformans en Arxula adeninivorans is gekies vir sifting. Saccharomyces cerevisiae is ingesluit as 'n positiewe kontrole aangesien trippellaag rotavirus-agtige partikels (tlRLPs) voorheen suksesvol in hierdie gis geproduseer is. Al nege gisstamme is suksesvol getransformeer met pKM177 vektore wat gis geoptimaliseerde kodon VP6 oopleesrame bevat. Daar was egter slegs ses gisstamme waarin positiewe VP6 ORF integrasie gevind is. Die oorblywende drie gisstamme het higromisien B integrasie getoon, wat daarop dui dat die vektore suksesvol geïntegreer het in hierdie gisstamme, maar dat VP6 oopleesraam verloor is. Integrasie van beide rotavirus VP2/6 oopleesrame was suksesvol vir al die gis stamme wat met die dubbele uitdrukkingsvektore getransformeer is. Rotavirus VP6 proteïenuitdrukking is suksesvol uitgevoer in bakteriële selle. Die positiewe kontrole het ʼn spesifieke reaksie getoon met poliklonale rotavirus teenliggaampies wat teen Nebraska calf diarrhoea rotavirus opgewek is, National Research Foundation (NRF), Poliomyelitis Research Foundation (PRF)

Published
2015

44. Cryptococcal 3-Hydroxy Fatty Acids Protect Cells Against Amoebal Phagocytosis

Author

Madu, Uju L., primary, Ogundeji, Adepemi O., additional, Mochochoko, Bonang M., additional, Pohl, Carolina H., additional, Albertyn, Jacobus, additional, Swart, Chantel W., additional, Allwood, J. William, additional, Southam, Andrew D., additional, Dunn, Warwick B., additional, May, Robin C., additional, and Sebolai, Olihile M., additional

Published
2015
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46. Exploring carbon cycling in selected micro-organisms exposed to terrestrial carbon sequestration

Author

Chen, Jou-an, Van Heerden, Esta, Albertyn, Jacobus, Erasmus, Mariana, Chen, Jou-an, Van Heerden, Esta, Albertyn, Jacobus, and Erasmus, Mariana

Abstract

South Africa‘s economy is primarily driven by the utilization of coal to provide electricity, which results in more fossil fuels to be burnt that contributes towards global warming. The average daily temperature is estimated to rise between 1.1 to 6.4˚C by 2100. Carbon sequestration is a technology that can limit CO2 emission into the atmosphere by storing the CO2 away in oceans or the terrestrial subsurface. South Africa is focusing on geological storage at depths of 1 000 m. Limited scientific knowledge is available on the direct impact when large amounts of supercritical CO2 is injected into the subsurface. This includes the diversity of the deep subsurface microbial communities as well as their ecosystems and biogeochemical processes. The main aim of this project was to use selected deep subsurface micro-organisms (T. scotoductus, Geobacillus sp. GE-7 and Geobacillus sp. A12) and an organism that was known to grow under pressure (E. limosum) and introduce them to CCS conditions using a high pressure syringe incubator system. The identities of the selected micro-organisms were verified using molecular techniques, the genomes of these micro-organisms were retrieved and information regarding possible CO2 fixation pathways was verified using the Metacyc database collection. The CO2 fixation pathways of interest were the Calvin cycle, the reductive acetyl Co-enzyme A and the reductive citric acid cycles. Surprisingly, T. scotoductus and E. limosum were able to remain viable and metabolically active even at 100 bar and 100% CO2. This has never been previously reported in literature. However Geobacillus sp. GE-7 and Geobacillus sp. A12 could not remain viable when the pressure was increased from 2 bar to 20 bar or higher. The outcomes of this study indicate that the interactions between supercritical CO2 and the subsurface organisms should be considered as biogeochemical cycling. However, these interactions in the subsurface are still relatively unknown and the availab

Published
2014

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