The role of micro-organisms in the production of semiochemicals in the interdigital secretion of the bontebok, Damaliscus pygargus pygargus

Scott, Gary Terri (2004-03)

Thesis (MSc)--Stellenbosch University, 2004.

Thesis

ENGLISH ABSTRACT: Bontebok, Damaliscus pygargus pygargus, formerly classified as D. dorcas dorcas, are territorial animals with interdigital glands between the toes of the forelegs. Males regularly defecate on dung heaps, on which they often lie, to communicate with other members of their species. They also communicate by means of visual displays, scent marking and occasionally with scraping or pawing of dung heaps. It is assumed that scent marking with the interdigital secretion serves to define territories frequented by these antelope. These glands secrete a complex mixture of volatile and non-volatile compounds and the volatile compounds in the secretion serve as a chemical signal for other bontebok. It has been suggested that the interdigital secretion is not produced in its final composition by the interdigital gland alone, but that microbial activity is responsible for many of the compounds present in the secretion. In general, many compounds can be attributed to the by-products of microbial hydrolysis of triglycerides, a common characteristic of sebum. It is well documented that micro-organisms inhabit the deep recesses of sebaceous glands and the presence of micro-organisms has been found to be consistent in all antelope exocrine glandular areas. This study involved the chemical characterisation of the volatile metabolites produced in vitro by micro-organisms from the interdigital cavity of the bontebok. Various comparative studies were made, one of which was comparison of the metabolites produced by the individual microbial species as well as the total community of bacteria incubated in different media. A comparison of the compounds identified in the interdigital secretion and the metabolites produced by the micro-organisms in the different media was also made. The volatile metabolite extracts of the individual bacterial species and of the total community were chemically characterised by low-resolution gas chromatography-mass spectroscopy. Classes of compounds identified from the volatile metabolite extracts include: • Acids - Aliphatic (saturated and unsaturated) • Alcohols - Aliphatic (saturated and unsaturated) • Aldehydes - Aliphatic (saturated and unsaturated) • Aromatic compounds • Ketones - Aliphatic (saturated and unsaturated) • Pyrazines • Dimethyldisulphide • Squalene and cholesterol Several qualitative differences were found between the compounds identified in the volatile metabolite extracts of the micro-organisms when incubated in tryptic soy broth (TSB) and minimal salt medium (MSM). In particular, when the microbes were incubated in TSB medium a number of pyrazines were found that were not present when utilising MSM as a medium. Additional qualitative differences were found between the compounds identified in the metabolite extracts of the individual bacterial species and the total community of bacteria, when incubated in both TSB and MSM media. A comparison of the interdigital secretion and the metabolite extracts of the microbial communities incubated in TSB and MSM revealed that many compounds produced in MSM corresponded to the compounds identified in the interdigital secretion. These corresponding compounds were found to be saturated and unsaturated acids, aldehydes and squalene. Furthermore, there was only one corresponding compound in the case of TSB as medium.

AFRIKAANSE OPSOMMING: Die bontebok, Damaliscus pygargus pygargus, voorheen geklassifiseer as D. dorcas dorcas, is 'n territoriale dier met interdigitale kliere tussen die kloutjies van die voorpote. Ramme ontlas gereeld op mishope, waarop hulle dikwels lê, om met ander lede van die spesie te kommunikeer. Hulle kommunikeer ook deur middel van visuele seine, reukmerking en soms deur mishope met die voorpote te kap of te skraap. Reukmerking met die interdigitale afskeiding dien klaarblyklik om gebiede wat deur hierdie diere bewoon word, af te baken. Die interdigitale kliere skei 'n komplekse mengsel van vlugtige en nie-vlugtige verbindings af en die vlugtige verbindings dien as chemiese sein vir ander bontebokke. Die vermoede bestaan dat die interdigitale klier nie alleen verantwoordelik is vir die finale samestelling van die interdigitale afskeiding nie, maar dat mikrobiese aktiwiteit bydra tot die produksie van baie van die verbindings wat in die afskeiding aanwesig is. Sekere verbindings kan in die algemeen toegeskryf word aan die vorming van die neweprodukte van mikrobiese hidrolise van trigliseriede, 'n algemene eienskap van sebum. Dit is bekend dat die diep holtes van vetkliere 'n goeie teelaarde is vir mikroorganismes en daar is gevind dat mikroorganismes feitlik deurgaans voorkom in alle anteloop eksokriene klierareas. Hierdie studie behels die chemiese karakterisering van die vlugtige metaboliete wat in vitro deur mikroorganismes van die interdigitale klierholte van die bontebok geproduseer word. Verskeie vergelykende studies is uitgevoer waarvan een die vergelyking was van die metaboliete wat deur die individuele mikrobiese spesies sowel as die totale gemeenskap van bakterieë geproduseer word tydens inkubasie in verskillende media. Vergelyking van die verbindings wat in die interdigitale afskeiding geïdentifiseer is met die metaboliete wat in verskillende media geproduseer is, het ook deel van die studie uitgemaak. Die vlugtige metaboliet ekstrakte van die individuele bakteriese spesies en van die totale gemeenskap is chemies gekarakteriseer deur middel van laeresolusie gaschromatografie-massaspektrometrie. Die volgende groepe verbindings is onder andere in die vlugtige metaboliet ekstrakte geïdentifiseer: • Sure - Alifaties (versadig en onversadig) • Alkohole - Alifaties (versadig en onversadig) • Aldehiede - Alifaties (versadig en onversadig) • Aromatiese verbindings • Ketone - Alifaties (versadig en onversadig) • Pirasiene • Dimetieldisulfied • Skwaleen en cholesterol Verskeie kwalitatiewe verskille is gevind tussen die verbindings wat geïdentifiseer is in die vlugtige metaboliet ekstrakte van die mikroorganismes onderskeidelik in TSB medium en MSM geïnkubeer. Opvallend was byvoorbeeld die voorkoms van pirasiene in gevalle waar mikroorganismes in TSB medium geïnkubeer is, terwyl hierdie groep verbindings afwesig was wanneer MSM gebruik is. Onderlinge kwalitatiewe verskille is ook gevind tussen die verbindings wat geïdentifiseer is in die metaboliet ekstrakte van die individuele bakteriese spesies en die totale gemeenskap van bakterieë, wanneer in TSB medium sowel as in MSM geïnkubeer is. Vergelyking van die verbindings in die interdigitale afskeiding en in die metaboliet ekstrakte van die mikrobiese gemeenskappe, het getoon dat 'n aantal verbindings wat in MSM geproduseer is, ooreenstem met verbindings wat in die interdigitale afskeiding geïdentifiseer is. Daar is gevind dat hierdie verbindings versadigde en onversadigde sure en aldehiede en skwaleen is. Met TSB as medium was daar slegs een ooreenstemmende verbinding.

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