Biodiversity of yeasts associated with mosquito larvae from different water habitats
| dc.contributor.advisor | Botha, Alfred | en_ZA |
| dc.contributor.advisor | Roets, Francois | en_ZA |
| dc.contributor.author | Steyn, Annica | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Microbiology. | en_ZA |
| dc.date.accessioned | 2016-03-09T14:00:46Z | |
| dc.date.available | 2019-12-12T03:00:11Z | |
| dc.date.issued | 2016-03 | |
| dc.description | Thesis (MSc)--Stellenbosch University, 2016. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The success of mosquitoes in nature has been linked to their microbiota and bacteria in particular. Yet, knowledge on their symbioses with yeasts is lacking. To explore possible associations, culturable yeasts were isolated from wild Culex larvae, and their habitat water, from sites that differed in land-use type such as natural forests, plantations, pristine river pools and urban sites. Isolated yeasts were classified using restriction fragment length polymorphism (RFLP) analyses and identified by sequencing the D1/D2 region of the 26S rRNA gene. Fungal representative strains of Aureobasidium, Candida, Cryptococcus, Debaryomyces, Galactomyces, Hannaella, Hypocreales, Lecythophora, Meyerozyma, Pichia, Rhodosporidium, Rhodotorula, Trichosporon and Wickerhamomyces were isolated from the larvae. These were the first records of the yeast microbiota from wild mosquito larvae and showed that they may harbour potential clinically relevant yeast species, including the well- known opportunistic human pathogen Candida albicans. Water quality of sites was analyzed for different physicochemical parameters and related to yeast assemblages in water and in larvae. The effects of physicochemical characteristics were more pronounced on yeast assemblages occurring in the habitat waters than on the endogenous yeasts occurring within the larvae. Larvae also harboured a higher than expected abundance of ascomycetous, fermentative and non-pathogenic yeasts in their gut, in relation to water from their habitat, suggesting some sort of selection pressure on yeast gut symbionts. Significant influences of land-use types on yeast assemblages were only detected for water-associated yeasts. These results indicated that larvae may act as the dominant factor that determines their endogenous yeast assemblages. Selected yeast strains of C. albicans, Candida glabrata, Candida pseudolambica, Cryptococcus gattii, Metschnikowia bicuspidata, Saccharomyces cerevisiae and Wickerhamomyces anomalus were also used as sole feed in a 21 day feeding experiment, during which the effect of each was tested on the ontogeny of Culex pipiens. Although most yeasts supported larval growth in a similar manner to the positive control S. cerevisiae strain, the different yeast strains impacted differently on Cx. pipiens ontogeny. Notably, survival and pupation of larvae were negatively impacted by a representative strain of the primary pathogen C. gattii, signifying that some yeasts are natural antagonists of mosquitoes. In addition, the microbiota of newly emerged adults was examined and the results supported the hypothesis of microbial reduction/ elimination during adult emergence for this species, thereby questioning the role of mosquitoes in yeast dispersal amongst different habitats. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die sukses van muskiete in die natuur is al toegeskryf aan hul mikrobiota en veral bakterieë. Tog ontbreek die kennis oor hul simbioses met giste. Om moontlike verbintenisse te ondersoek is kweekbare giste geïsoleer vanuit wilde Culex larwes vanaf verskillende grondgebruik tipes soos natuurlike woude, plantasies, ongerepte rivierpoele en stedelike terreine. Giste was ook geïsoleer vanuit die waters van hierdie habitatte. Die giste was geklassifiseer met restriksie fragment lengte polimorfisme (RFLP) analises en geïdentifiseer deur volgordebepaling van die D1/D2 streek wat behoort aan die 26S rRNA geen. Fungale verteenwoordiger stamme van Aureobasidium, Candida, Cryptococcus, Debaryomyces, Galactomyces, Hannaella, Hypocreales, Lecythophora, Meyerozyma, Pichia, Rhodosporidium, Rhodotorula, Trichosporon en Wickerhamomyces was geïsoleer vanuit die larwes. Ons resultate lewer die eerste verslag van die gis mikrobiota vanaf wilde muskiet larwes en dui aan dat hulle potensiële klinies relevante giste kan huisves, insluitende die bekende opportunistiese menslike patogeen Candida albicans. Die waterkwaliteit van terreine is ontleed vir verskillende fisies-chemiese parameters en daar was bepaal of hierdie parameters verband hou met gis bevolkings vanaf die water en larwes. Die fisies-chemiese eienskappe van die water het ̳n groter uitwerking gehad op die gis populasies wat in die habitat waters voorgekom het, as op die endogene giste wat in die larwes teenwoordig was. Larwes se ingewande het, in vergelyking met hul habitat waters, ̳n hoër as verwagte oorvloed van askomisete, fermentatiewe en nie-patogeniese giste gehuisves, aanduidend van ̳n moontlike seleksie druk wat uitgevoer word op die gis simbionte van die ingewande. Beduidende invloede van grondgebruik tipes op gis populasies was slegs waargeneem vir water-geassosieerde giste. Hierdie resultate het daarop gedui dat die larwes moontlik self kan optree as die deurslaggewende faktor in die bepaling van hul endogene gis bevolkings. Daarbenewens is stamme van C. albicans, Candida glabrata, Candida pseudolambica, Cryptococcus gattii, Metschnikowia bicuspidata, Saccharomyces cerevisiae en Wickerhamomyces anomalus gebruik as enigste voer gedurende ̳n voedingseksperiment van 21 dae waartydens elk se effek op die ontogenie van Culex pipiens getoets is. Alhoewel giste meestal die groei van larwes ondersteun het op ̳n soortgelyke wyse as die positiewe kontrole S. cerevisiae stam, het verskillende giste die ontogenie van Cx. pipiens verskillend beïnvloed. Oorlewing en verpopping van larwes was veral negatief beïnvloed deur ̳n verteenwoordigende stam van die primêre patogeen C. gattii, aanduidend dat sekere giste natuurlike antagoniste van muskiete is. Daarbenewens was die gevolgelike mikrobiota van nuwe volwasse muskiete ondersoek en die hipotese van mikrobiese vermindering/ uitskakeling tydens volwasse opkoms van hierdie spesie is deur die resultate gesteun en sodoende is die rol van muskiete in gis-verspreiding tussen verskillende habitatte bevraagteken. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2019-12-12 | |
| dc.format.extent | xiv, 135 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/98285 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Mosquito microbiota | en_ZA |
| dc.subject | Mosquito nutrition | en_ZA |
| dc.subject | Yeast diversity | en_ZA |
| dc.subject | Pathogenic yeasts | en_ZA |
| dc.subject | Land-use type | en_ZA |
| dc.subject | Water physicochemical characteristics | en_ZA |
| dc.subject | Mosquitoes -- Larvae | en_ZA |
| dc.subject | Mosquitoes -- Habitat | en_ZA |
| dc.subject | Bacteria | en_ZA |
| dc.subject | Mosquitoes -- Effect of habitat modification on | en_ZA |
| dc.subject | Gut microbiota | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Biodiversity of yeasts associated with mosquito larvae from different water habitats | en_ZA |
| dc.type | Thesis | en_ZA |
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