réalisé en cotutelle avec la Faculté des Sciences de Tunis, Université Tunis El Manar. / Le pois chiche (Cicer arietinum L.) a l’avantage de pouvoir assimiler l'azote atmosphérique grâce à son association symbiotique avec des bactéries du genre Mesorhizobium. Malgré cet effet bénéfique sur les systèmes culturaux, le pois chiche réduit parfois la productivité du blé qui la suit. Cet effet négatif du pois chiche pourrait provenir d’une réaction allélopathique à ses exsudats racinaires ou résidus, ou de changements inopportuns dans la communauté microbienne du sol induits par la plante. L'amélioration des interactions symbiotiques du pois chiche pourrait améliorer la performance économique et environnementale des systèmes culturaux basés sur le blé. L’objectif à long terme de ce travail est d'améliorer l’influence du pois chiches sur son environnement biologique et sur la productivité du système cultural. À court terme, nous voulons 1) vérifier l'effet des champignons endophytes sur la performance de cultivars de pois chiche de type desi et kabuli, particulièrement en conditions de stress hydrique, ainsi que sur celle d’une culture subséquente de blé dur, 2) identifier des cultivars de pois chiche capables d’améliorer la qualité biologique de sols cultivés, 3) vérifier que des composés biologiquement actifs sont présents dans les racines des différents cultivars de pois chiches et 4) définir la nature de l’activité (stimulation ou inhibition) des ces composés sur les champignons endomycorhiziens à arbuscules (CMA), qui sont des microorganismes bénéfiques du sol reconnus. L’inoculation du pois chiche avec des champignons endophytes indigènes en serre a augmenté la tolérance à la sécheresse du cultivar de type kabuli à feuille simple CDC Xena et amélioré la nutrition azotée et phosphatée d’un cultivar de type desi, cv. CDC Nika, cultivé en conditions de stress hydrique. La germination des graines de blé dur fut meilleure lorsque celles-ci étaient semées dans les débris de pois chiche inoculé de type kabuli. Le sol dans lequel le génotype de pois chiche à feuille simple CDC Xena fut cultivé mais duquel tout le matériel végétal de pois chiche fut retiré a fortement inhibé la germination des semences de blé dur, ce qui suggère un effet des exsudats racinaires sur la communauté microbienne du sol associée à cette variété de pois chiche. En champ, les cultivars de pois chiche ont influencé différemment la composition des communautés de champignons de la rhizosphère. Les espèces de champignons pathogènes étaient infréquentes et les espèces saprotrophiques et de CMA étaient fréquentes dans la zone des racines du cultivar de type desi CDC Anna. L’effet des composés contenus dans les fractions séparées par HPLC et solubles en solution de méthanol à 25% et 50% de l’extrait racinaire de ce cultivar sur la germination de spores de CMA a été testé in vitro. Les deux espèces de CMA utilisées ont répondu différemment à l’exposition aux composés testés, révélant un mécanisme impliqué dans l’association préférentielle entre les plantes hôtes et les CMA qui leurs sont associés. Nous concluons que le génotype de pois chiche influence la composition de la communauté microbienne qui lui est associée et que cette influence est reliée au moins en partie aux molécules bioactives produites par les racines de la plante. D’autre part, la productivité du pois chiche et de la culture subséquente pourrait être favorisée par la manipulation de leurs champignons endophytes par inoculation. / Chickpea (Cicer arietinum L.) has the ability to bring free N into cropping systems, but is only a fair rotation crop, leading to lower yield in following wheat crops, as compared to medic, vetch or lentil. The negative effects of a chickpea plant on the following wheat crops could come from chickpea root exudates, their residues or their influence on the soil microbial community. The identification of chickpea cultivars best able to promote soil biological quality and the growth of a subsequent crop in rotation will help farmers in selecting better crop rotations and, thus, will improve crop management in soil zone growing chickpea. The global objective of this research is to improve the fitness of chickpea crops to their biological environment and to improve the ability of the plant to enhance soil biological quality. The specific objectives were (1) to verify that the productivity of chickpea and subsequent crops could be promoted through the inoculation by some indigenous endophytic fungi particularly under drought stress conditions (2) to verify the existence of variation in the rhizospheric associations of field-grown chickpea, as it is a necessary condition for the selection of genotypes with improved compatibility with beneficial microorganisms. (3) to identify the biologically active compounds present in the root extracts of chickpea cultivars with contrasting phenotypes, and assess their effect on beneficial and pathogenic soil microorganisms. The greenhouse experiments show that inoculation with indigenous endophytes increased drought tolerance of the unifoliate Kabuli chickpea CDC Xena and the N and P nutrition of the drought stressed Desi chickpea CDC Nika. Inoculation of both Kabuli chickpea varieties with indigenous endophytes improved wheat seeds germination in tissues amended soil. Residue-free soil previously growing the unifoliate Kabuli chickpea CDC Xena strongly inhibited durum seed germination suggesting an effect of root exudates on the soil microbial community, with this Kabuli chickpea variety. In a field experiment, the fungal diversity in cultivated Prairie dryland appeared to host a large array of fungal groups known to reduced plant nutrient, water and biotic stresses, and chickpea genotypes influenced differently the composition and biomass of the soil microbial community. The Desi chickpea CDC Anna was associated with high diversity of arbuscular mycorrhizal fungi (AMF) and culturable fungi, favored the proliferation of soil bacteria and fungal genus hosting biocontrol agents, and developed high AM root colonization level, as compared to the three Kabuli genotypes examined. The HPLC fractions of the roots of chickpea cultivar CDC Anna were recovered and the effects of these fractions on AM fungal spore germination were assayed in multi-well plates. Root extract fractions affect in a different ways the percentage of spores’ germination of Glomus etunicatum and Gigaspora Rosea. We concluded that the genotype of chickpea plants influences the composition of the associated microbial community, and this influence may be related to molecular signals produced by the plants. Furthermore, the productivity of chickpea and subsequent crops could be promoted through the inoculation with indigenous endophytic fungi.

Le pois chiche (Cicer arietinum L.) a l’avantage de pouvoir assimiler l'azote atmosphérique grâce à son association symbiotique avec des bactéries du genre Mesorhizobium. Malgré cet effet bénéfique sur les systèmes culturaux, le pois chiche réduit parfois la productivité du blé qui la suit. Cet effet négatif du pois chiche pourrait provenir d’une réaction allélopathique à ses exsudats racinaires ou résidus, ou de changements inopportuns dans la communauté microbienne du sol induits par la plante. L'amélioration des interactions symbiotiques du pois chiche pourrait améliorer la performance économique et environnementale des systèmes culturaux basés sur le blé. L’objectif à long terme de ce travail est d'améliorer l’influence du pois chiches sur son environnement biologique et sur la productivité du système cultural. À court terme, nous voulons 1) vérifier l'effet des champignons endophytes sur la performance de cultivars de pois chiche de type desi et kabuli, particulièrement en conditions de stress hydrique, ainsi que sur celle d’une culture subséquente de blé dur, 2) identifier des cultivars de pois chiche capables d’améliorer la qualité biologique de sols cultivés, 3) vérifier que des composés biologiquement actifs sont présents dans les racines des différents cultivars de pois chiches et 4) définir la nature de l’activité (stimulation ou inhibition) des ces composés sur les champignons endomycorhiziens à arbuscules (CMA), qui sont des microorganismes bénéfiques du sol reconnus. L’inoculation du pois chiche avec des champignons endophytes indigènes en serre a augmenté la tolérance à la sécheresse du cultivar de type kabuli à feuille simple CDC Xena et amélioré la nutrition azotée et phosphatée d’un cultivar de type desi, cv. CDC Nika, cultivé en conditions de stress hydrique. La germination des graines de blé dur fut meilleure lorsque celles-ci étaient semées dans les débris de pois chiche inoculé de type kabuli. Le sol dans lequel le génotype de pois chiche à feuille simple CDC Xena fut cultivé mais duquel tout le matériel végétal de pois chiche fut retiré a fortement inhibé la germination des semences de blé dur, ce qui suggère un effet des exsudats racinaires sur la communauté microbienne du sol associée à cette variété de pois chiche. En champ, les cultivars de pois chiche ont influencé différemment la composition des communautés de champignons de la rhizosphère. Les espèces de champignons pathogènes étaient infréquentes et les espèces saprotrophiques et de CMA étaient fréquentes dans la zone des racines du cultivar de type desi CDC Anna. L’effet des composés contenus dans les fractions séparées par HPLC et solubles en solution de méthanol à 25% et 50% de l’extrait racinaire de ce cultivar sur la germination de spores de CMA a été testé in vitro. Les deux espèces de CMA utilisées ont répondu différemment à l’exposition aux composés testés, révélant un mécanisme impliqué dans l’association préférentielle entre les plantes hôtes et les CMA qui leurs sont associés. Nous concluons que le génotype de pois chiche influence la composition de la communauté microbienne qui lui est associée et que cette influence est reliée au moins en partie aux molécules bioactives produites par les racines de la plante. D’autre part, la productivité du pois chiche et de la culture subséquente pourrait être favorisée par la manipulation de leurs champignons endophytes par inoculation. / Chickpea (Cicer arietinum L.) has the ability to bring free N into cropping systems, but is only a fair rotation crop, leading to lower yield in following wheat crops, as compared to medic, vetch or lentil. The negative effects of a chickpea plant on the following wheat crops could come from chickpea root exudates, their residues or their influence on the soil microbial community. The identification of chickpea cultivars best able to promote soil biological quality and the growth of a subsequent crop in rotation will help farmers in selecting better crop rotations and, thus, will improve crop management in soil zone growing chickpea. The global objective of this research is to improve the fitness of chickpea crops to their biological environment and to improve the ability of the plant to enhance soil biological quality. The specific objectives were (1) to verify that the productivity of chickpea and subsequent crops could be promoted through the inoculation by some indigenous endophytic fungi particularly under drought stress conditions (2) to verify the existence of variation in the rhizospheric associations of field-grown chickpea, as it is a necessary condition for the selection of genotypes with improved compatibility with beneficial microorganisms. (3) to identify the biologically active compounds present in the root extracts of chickpea cultivars with contrasting phenotypes, and assess their effect on beneficial and pathogenic soil microorganisms. The greenhouse experiments show that inoculation with indigenous endophytes increased drought tolerance of the unifoliate Kabuli chickpea CDC Xena and the N and P nutrition of the drought stressed Desi chickpea CDC Nika. Inoculation of both Kabuli chickpea varieties with indigenous endophytes improved wheat seeds germination in tissues amended soil. Residue-free soil previously growing the unifoliate Kabuli chickpea CDC Xena strongly inhibited durum seed germination suggesting an effect of root exudates on the soil microbial community, with this Kabuli chickpea variety. In a field experiment, the fungal diversity in cultivated Prairie dryland appeared to host a large array of fungal groups known to reduced plant nutrient, water and biotic stresses, and chickpea genotypes influenced differently the composition and biomass of the soil microbial community. The Desi chickpea CDC Anna was associated with high diversity of arbuscular mycorrhizal fungi (AMF) and culturable fungi, favored the proliferation of soil bacteria and fungal genus hosting biocontrol agents, and developed high AM root colonization level, as compared to the three Kabuli genotypes examined. The HPLC fractions of the roots of chickpea cultivar CDC Anna were recovered and the effects of these fractions on AM fungal spore germination were assayed in multi-well plates. Root extract fractions affect in a different ways the percentage of spores’ germination of Glomus etunicatum and Gigaspora Rosea. We concluded that the genotype of chickpea plants influences the composition of the associated microbial community, and this influence may be related to molecular signals produced by the plants. Furthermore, the productivity of chickpea and subsequent crops could be promoted through the inoculation with indigenous endophytic fungi. / réalisé en cotutelle avec la Faculté des Sciences de Tunis, Université Tunis El Manar.

Department of Microbiology / PhD (Microbiology) / Human herpes virus type 8 (HHV-8), also known as Kaposi’s sarcoma associated herpes virus (KSHV), is the etiologic agent of Kaposi’s sarcoma (KS), and AIDS related Kaposi’s sarcoma (AIDS-KS). HHV-8 which is a member of the Herpesviridae family, exhibits extensive genetic diversity globally. In endemic regions, infection with HHV-8 occurs very early on in life, which is an indication of both environmental and vertical routes of transmission. The advent of HIV leads to the classification of an AIDS-KS defining condition in HIV infections. This suggests that in regions where HIV and HHV-8 are endemic, KS may become common in a mature HIV epidemic. Just like the prevalence of HIV in Northern South Africa is generally high as in most regions of the country, as the HIV epidemic matures in South Africa, it is important to understand the burden and distribution of HHV-8 infection, and the likely genotypes infecting the population. The main objective of the thesis was to establish the epidemiology and infecting genotypes of HHV-8 in Northern South Africa (Limpopo Province), where no data exists. First, a systematic review of the literature was carried out for the entire African continent to determine the seroprevalence and genotype distribution of HHV-8 in all African countries (n=53). In this review, Sudan and South Sudan were considered as one country. Articles were searched using the PRISMA guideline and exported using an article grid. More than two-thirds (64%) of the studies reported on seroprevalence, 29.3% on genotypes; and 9.5% were on both seroprevalence and genotypes. About 45% (24/53) of the African countries had data on HHV-8 seroprevalence exclusively, and more than half (53%) had data on either seroprevalence or genotypes. Almost half (47%) of the countries had no data on HHV-8 infection. There was high heterogeneity in the types of tests and interpretation algorithms used in determining HHV-8 seropositivity across the different studies. Generally, seroprevalence ranged from 2.0% in a group of young children in Eritrea to 100% in a small group of individuals with KS in the Central Africa Republic and a larger group of KS in individuals in Morocco. Approximately, 16% of all the studies reported on children. The difference in seroprevalence across the African region was not significant (95% CI, X2 =0.86; p =0.35), although specifically, a relatively significant ETTA MASHU ELIZABETH, PHD IN MICROBIOLOGY|UNIVERSITY OF VENDA, 2019|VIII level of infection was observed in HIV-infected children. About 38% of the countries had data on K1 genotypes A, A5, B, C, F and Z which occurred at frequencies of 5.3%, 26.3%, 42.1%, 18.4%, 5.3% and 2.6% respectively. Twenty-three percent of the countries had data for K15 genotypes, whereas genotypes P, M and N occurred at frequencies of 52.2%, 39.1% and 8.7% respectively. Data on HHV-8 inter-genotype recombinant is scanty. Our finding suggests that HHV-8 is endemic on the entire African continent, and in HIV endemic regions, but there is need for a harmonized testing protocol for better understanding of HHV-8 seropositivity. HHV-8 genotype A5 and B for K1 gene and genotype P and M for K15 gene are the most predominant genotypes in Africa. The review, for the first time, has provided information on HHV-8 burden on the entire African continent, and suggests that vaccine development efforts for Africa should focus on genotypes B and P. The second component of the investigation focused on the burden of HHV-8 in an HIV population in Northern South Africa (Limpopo Province). Plasma from 3501 HIV infected individuals from 5 districts in Limpopo Province were assessed for antibodies to both the lytic antigen (ORFK8.1) and the latent antigen (ORF73). The distribution of infection was analyzed based on demographic, socioeconomic, and immunological parameters. Statistical inferences for significant differences were determined by Chisquare at a confidence interval of 95%. P-values less than 0.05 were considered significant. About 19.0% of the study population was positive for antibodies to either the lytic or latent antigens or both. Prevalence of antibodies to the lytic antigen was significantly higher than prevalence of antibodies to the latent antigen (17.3% vs 4.1%; p=0.0001). Significant differences were observed for age groups, racial population groups, districts and year of sample collection (p=<0.0001, p=<0.0001, p=<0.0001 and p=0.0385) respectively. Associations were found between both antigens in comparison to the different variables such as age group, racial population groups and districts (R2 value ranging between 0.886 and 1.0). The burden of HHV-8 has now been established for the first time in Northern South Africa. The third aspect of the investigation was a meta-analysis of HHV-8 seroprevalence in Southern Africa in order to understand the impact of geographical location (urban vs rural) on infection. The analysis revealed a significant association between urban settings and HHV-8 infection (p=0.0001). ETTA MASHU ELIZABETH, PHD IN MICROBIOLOGY|UNIVERSITY OF VENDA, 2019|IX The fourth component of the thesis examined the detection of HHV-8 antigen through polymerase chain reaction (PCR) in 534 participants in HIV infected and HIV noninfected populations. A selection of mouthwash DNA samples were subjected to Next Generation Sequencing (NGS) for subsequent genotype inference. Mouth wash samples were obtained from each consenting individual before eating or smoking, and their DNA was purified. A 233bp fragment of the ORF26 gene of HHV-8 was amplified by PCR. HHV-8 was detected in 150 of the 534 participants (28.1%). A significant difference in detection was observed for gender, HIV status, district and the level of education (p=0,0003; p=0.0094; p=0.0002 and p=0.0095) respectively. Consensus sequences were derived from NGS reads for 13 samples. The genotyping results revealed that genotype Q, B, E and N are the genotypes predominant in the study population. As such no mixed infections were detected. Therefore, from the investigations foregoing have demonstrated for the first time the following: (1) HHV-8 is endemic in the entire African continent, which suggest a coendemicity in regions already endemic for HIV; (2) HHV-8 is endemic in Northern South Africa; (3) Urban settings in Southern Africa are associated with high HHV-8 infection; (4) HHV-8 genotypes Q, B, E and N may be predominant in Northern South Africa, with B and P common on the entire African continent. Hence, studies should focus on the generation of full length HHV-8 genomes of the common genotypes to support the selection of genes for vaccine design and development. / NRF

MSc (Microbiology) / Department of Microbiology / BACKGROUND: Human papillomavirus (HPV) is a common sexually transmitted virus known to be a causative agent of cervical cancer (CC), one of the most frequent cancers in women worldwide. HPV is a double stranded DNA virus of approximately 7,900 bp; belonging to Papillomaviridae family. To date, about 202 low risk (LR) and high risk (HR) HPV genotypes have been identified. However, available vaccines against HPV infection are designed based on the most common known genotypes. Therefore, it is critical to understand the scope and diversity of HPV genotypes in all geographical locations which can help to inform the design and development of future vaccines. OBJECTIVE: The objective of this study was to describe the burden and diversity of HPV genotypes in a cohort of women in routine care in northern South Africa. METHODS: Eighty seven women consented to participate in the study and each provided a specimen for analysis. With the help of qualified health care practitioners, Aptima Cervical Specimen Collection and Transport Kit (Hologic, San Diego, CA) was used to collect cervical specimens from each study participant following the manufacturer’s procedure. Total DNA was purified from the cervical pellet using QIAamp DNA mini kit (Qiagen, Hilden, Germany) according to the manufacturer’s instructions. The purified DNA was then subjected to a single round conventional PCR in a reaction volume of 100 μl to amplify HPV L1 gene comprising of approximately 450 bp. A portion of each PCR amplicon from each participant was denatured, hybridized and genotyped using the Linear Array HPV genotyping Test Kit (Roche Molecular Systems, Inc. Branchburg, NJ USA). The kit is designed to detect 37 HPV genotypes (genotypes 6, 11, 16, 18, 26, 31, 33, 35, 39, 40, 42, 45, 51, 52, 53, 54, 55, 56, 58, 59, 61, 62, 64, 66, 67, 68, 69, 70, 71, 72, 73, 81, 82, 83, 84, IS39 and CP6108). To detect the HPV genotypes, the Linear Array (LA) reference guide was used for results interpretation following the manufacturer’s instructions. The other portion of each of the amplicons was subjected to next generation sequencing (NGS) using the Illumina MiniSeq platform. Using the Nextera XT DNA Library preparation kit, an initial input of 1ng genomic DNA was tagmented, cleaned up, normalized and pooled. The pooled library was then denatured with 0.1 N NaOH and diluted into a final volume of 500 μl at 1.8 pM then sequenced using the Local Run Manager option following the manufacturer’s instructions. The generated sequence data was downloaded into fastaQ format and analysed using Genious 11.0.5 software. RESULTS: Of the 87 participants, the overall proportion of women harbouring HPV DNA by linear array (LA) PCR was 23% (n=20). Of the 20, 16 (80%) were living with HIV. However, this difference was not significant (p=0.077). Genotyping data generated by Roche LA method was successful for all the 20 positive amplicons. In this study, 27 (73%) of the 37 HPV genotypes incorporated in the Roche Linear Array method were detected. The detected genotypes include: types 84, 83, 81, 73, 72, 71, 70, 69, 68, 66, 62, 61, 59, 54, 53, 52, 51, 45, 42, 39, 35, 26, 18, 16, 6, IS39 and CP6108. Most women (15/20;75%) harboured multiple infections compared to single infection. In terms of genotypes distribution, the most frequent genotypes detected LR HPV types in increasing order of frequency included HPV type 61 and 83 (12%), 62 (36%) and 81 (43%). On the other hand, HPV type 66, 53, 52, 51, 18 and 16 were the most common genotypes detected HR HPV types. In contrast, although genotyping data was successfully generated from 15 of 20 women (75%), NGS technology was seen to be more sensitive compared to Roche LA method. Nearly all the detected genotypes identified by the commercial kit were detected by NGS. In addition, NGS detected 10 namely: HPV types 11, 31, 33, 40, 55, 56, 58, 64, 67, and 82 that were not detected by the LA yet incorporated in the kit. Moreover, it was observed that NGS identified additional 6 HPV types including HPV types 2, 27, 30, 35, 85 and 102 not incorporated in the Roche LA kit. A similar distribution of HPV multiple infections was observed in the study population, however, high frequency of 93% (14 of 15) was detected by NGS. The proportion of women harbouring one or more of the 22 LR HPV types was 100% (n=15).The most frequent LR genotypes in increasing order of frequency was HPV type 62 and 70 (27%), 6 (40%) and 11 (47%). HPV types 40, 42, 54, 72, 64, and 81 were the least detected genotypes with n=1 (7%) each. Furthermore, the common combination observed among the participants was type 6 and 11. In contrast, the most frequent detected genotypes in the study population by NGS under the HR HPV types in increasing order of frequency include type 35 (21%), 39, 56 and 82 (29%), 68 (36%) and 51 (50%). In addition, HPV types 26, 31, 45, 53, 56, 58 and 66 were the least detected genotypes n=1 (7%) in the study population. HPV 39 and 68 were observed as the common combination detected under HR HPV types. Following genotyping by LA and NGS, the demographic and clinical data of all the 20 positive subjects by PCR were subjected to statistical analysis to determine the association between HPV positive DNA status and associated risk factors. Smoking status (p=0.000), age at first sexual intercourse (p=0.011), vaccination status (p=0.000), gender of sexual partner (p=0.000), highest level of education (p=0.004), marital status (p=0.008) and number of sexual partners (p=0.000) were found to be having a positive statistical association. CONCLUSION: Amplification of targeted HPV DNA from cervical specimens demonstrated the presence of HPV infection in the study cohort, with a proportion of 23%. The findings illustrate that there is a diversity of HPV genotypes prevalent in the study population as shown by Roche LA and NGS methods. However, the NGS method was observed to be more sensitive than Roche LA in detecting HPV genotypes. Furthermore, NGS identified 6 additional HPV types not incorporated in the Roche LA. Thus, there are genotypes that may be present in the study population that the Roche commercial kit may fail to detect. Therefore, is it imperative to use both genotyping methods to confirm HPV genotypes. / NRF