The occurrence and physiology of Hyphopichia heimii, associated with beetle frass from Olea europaea subsp. cuspidata
| dc.contributor.advisor | Botha, Alfred | en_ZA |
| dc.contributor.advisor | Roets, Francois | en_ZA |
| dc.contributor.author | Asmus, Justin Joseph | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Microbiology. | en_ZA |
| dc.date.accessioned | 2020-02-24T16:33:13Z | |
| dc.date.accessioned | 2020-04-28T15:11:59Z | |
| dc.date.available | 2020-02-24T16:33:13Z | |
| dc.date.available | 2020-04-28T15:11:59Z | |
| dc.date.issued | 2020-03 | |
| dc.description | Thesis (MSc)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Bark beetles are destructive insect pests that pose a threat to natural forest and orchard ecosystems. It is well known that the ecological success of these insects depends on their symbioses with a range of microorganisms including bacteria and filamentous fungi. Recently, it was demonstrated that unicellular fungi, called yeasts, may also form symbioses with bark beetles. Several studies revealed that bark beetles, such as Dendroctonus frontalis and Dendroctonus ponderosae, are intimately associated with yeasts throughout their life cycles. It was suggested that these unicellular fungi may play vital roles in beetle nutrition, detoxification of host tree chemicals and may possibly influence attack behaviour of these insects. Nevertheless, few studies have attempted to investigate the functional roles of yeasts associated with bark beetles. Studies on the yeast symbionts of beetles could provide a better understanding of the symbioses that exist between trees, bark beetles and their associated microbial symbionts. This study was aimed at investigating the diversity of yeasts, culturable on a benomyl-containing selective medium, that occur in beetle frass originating from wild olive trees growing at several locations in Stellenbosch, South Africa. The yeasts able to grow on the isolation medium represented 28 species, of which 29% were ascomycetous species, while the majority (71%) were basidiomycetous species. The most dominant yeasts appearing frequently on the isolation plates prepared from the frass were the basidiomycetes Colacogloea philyla and an undescribed species, Cryptococcus sp. 3, as well as the rare ascomycetous yeast, Hyphopichia heimii. Using enzyme plate assays, it was found that the basidiomycetous yeast species, as opposed to the representatives of H. heimii, frequently demonstrated wood degrading abilities, by showing hemicellulosic enzymatic activity on the plates. All representatives of H. heimii, C. philyla and Cryptococcus sp. 3 however, were able to assimilate simple carbon sources (e.g. sucrose and cellobiose) that may occur within frass or vascular tissues of the olive trees. It was also found that the representatives of H. heimii and C. philyla were able to produce the plant growth-promoting factor indole acetic acid (IAA), with the highest producer being H. heimii CAB 1593 (3.062 ± 0.250 μg/log CFU) which indicated that these yeasts could be of benefit for their tree hosts. Sterol analysis of the dominant yeasts in the frass indicated that ascomycetes and basidiomycetes produced comparable quantities of ergosterol ranging from 1.365 ± 0.118 to 24.569 ± 0.950 mg/g dry cell weight and were therefore similar with regard to their potential to fulfil the dietary sterol requirements of bark beetles. In addition, it was found that H. heimii was able to convert cis-verbenol to verbenone and may therefore potentially affect beetle behaviour. To conclude, this study has provided tentative evidence of a tripartite symbiosis between the ascomycetous yeast, H. heimii, olive trees and bark beetles. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Baskewers is vernietigende insekplae wat die natuurlike ekosisteme van woud- en boorde bedreig. Dit is welbekend dat die ekologiese sukses van hierdie insekte afhang van hul simbiose met 'n verskeidenheid mikroörganismes, insluitend bakterieë en fungi. Dit was onlangs aangetoon dat eensellige fungi, ook bekend as giste, simbiose met baskewers kan vorm. Verskeie studies het bewys dat baskewers, byvoorbeeld Dendroctonus frontalis en Dendroctonus ponderosae, nou geassosieer is met giste gedurende hul lewenssiklus. Verder was dit ook voorgestel dat hierdie eensellige fungi 'n belangrike rol in kewervoeding en detoksifikasie van chemikalieë afkomstig van die gasheerboom speel. Daar is ook 'n moontlikheid dat hierdie eensellige fungi 'n invloed kan hê op die aanvalsgedrag van kewers. Nietemin het min studies al voorheen probeer om die funksionele rolle van giste wat met baskewers geassosieer word, te ondersoek. Daarom is dit moontlik dat studies oor die gis-simbionte van kewers 'n beter begrip kan bied van die simbiose wat tussen bome, baskewers en hul gepaardgaande mikrobiese simbionte bestaan. Hierdie studie het ten doel gehad om die verskeidenheid giste, wat gekweek kan word op 'n benomielbevattende selektiewe medium te ondersoek, wat voorkom in kewer boorsels afkomstig van wilde olyfbome wat op verskillende plekke in Stellenbosch, Suid-Afrika groei. Die giste wat op die isolasiemedium kon groei, het 28 spesies uitgemaak, waarvan 29% askomisete spesies was, terwyl die meerderheid (71%) basidiomisete spesies was. Die mees dominante giste wat gereeld op die isolasieplate van die boorsels verskyn het, was die basidiomisete Colacogloea philyla en 'n onbeskryfde spesie, Cryptococcus sp 3, sowel as die seldsame askomisete gis, Hyphopichia heimii. Deur gebruik te maak van ensiemplaattoetse is daar gevind dat die basidiomisete gisspesies, in teenstelling met die verteenwoordigers van H. heimii, gereeld houtafbrekende vermoëns getoon het, deur hemisellulose ensiematiese aktiwiteit op die plate te toon. Alle verteenwoordigers van H. heimii, C. philyla en Cryptococcus sp. 3 was egter in staat om eenvoudige koolstofbronne (d.w.s. sukrose en sellobiose) te assimileer wat in boorsels of vaatweefsel van die olyfbome kan voorkom. Daar is ook gevind dat die verteenwoordigers van H. heimii en C. philyla die plantgroei-bevorderende faktor indool-asynsuur (IAA) kon produseer, met die hoogste produsent H. heimii CAB 1593 (3.062 ± 0.250 μg/log CFU) wat aangedui het dat hierdie giste tot voordeel van hul gasheerbome sou wees. Sterolanalise van die dominante giste in die fras het aangedui dat askomisete en basidiomisete vergelykbare hoeveelhede ergosterol geproduseer het, wat wissel van 1,365 ± 0,118 tot 24,569 ± 0,950 mg/g droë selgewig, en dus soortgelyk was ten opsigte van hul potensiaal om aan die dieetsterolvereistes van bas kewers te voldoen. Daarbenewens is gevind dat H. heimii cis-verbenol in verbenone kon omskakel en daarom moontlik 'n invloed op die gedrag van kewers kan hê. Ter afsluiting het hierdie studie tentatiewe bewyse gelewer van 'n driepartysimbiose tussen die askomisete gis, H. heimii, olyfbome en die baskewer. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2023-12-20 | |
| dc.format.extent | 148 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/108393 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Microbiology | en_ZA |
| dc.subject.lcsh | Bark beetles -- Behavior | en_ZA |
| dc.subject.lcsh | Hyphopichia heimii -- Physiology | en_ZA |
| dc.subject.lcsh | Olive -- Breeding -- South Africa -- Stellenbosch | en_ZA |
| dc.subject.lcsh | Olive -- Growth | en_ZA |
| dc.subject.lcsh | Olive trees -- Diseases and pests -- South Africa -- Stellenbosch | en_ZA |
| dc.subject.name | UCTD | en_ZA |
| dc.title | The occurrence and physiology of Hyphopichia heimii, associated with beetle frass from Olea europaea subsp. cuspidata | en_ZA |
| dc.type | Thesis | en_ZA |