Search

Plant growth-promoting bacteria (PGPB) are of increased interest as they offer sustainable alternatives to the more common chemical fertilisers. Research, however, has increased into the use of PGPB as bioinoculants to improve yields. Legumes are known to interact with diazotroph PGPB which increase nutrient uptake, prevent pathogenic infections, and actively fix nitrogen. This study aimed to comprehensively describe PGPB associated with legumes grown in Namibia through analysis of the site-specific bacterial microbiomes. In the present study, we used the 16S rRNA sequencing approach to determine the structure of rhizosphere, root, and seed endosphere microbiomes of five drought-tolerant legume species: Macrotyloma uniflorum, Vigna radiata, Vigna aconitifolia, Vigna unguiculata and Lablab purpureus. Several important phyla were identified including Actinobacteriota, Bacteroidota, Firmicutes, Proteobacteria and Verrucomicrobiota. Overall, Proteobacteria was the most abundant phylum followed by Actinobacteria. The most important genera identified were Bacillus, Mesorhizobium, Pseudomonas, Bradyrhizobium and the Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium group. The relative abundance of these genera varied across sample types and legume species. This study identified important diazotrophs across all the legume species. Bacillus, an important PGPB, was found to be the most abundant genus among all the niches analysed and legume species, while Rhizobium spp. was particularly enriched in roots. This study ultimately provides previously undescribed information on legume-associated bacterial communities in Namibia.

The increase in dryland agriculture elicits the need to develop sustainable practices that improve crop yield and protect soil fertility. The use of biofertilisers adapted to nutrient deficient soils and arid climates would help achieve this. In this review, the use of plant growth-promoting bacteria is explored as a possible solution to the current state of dryland agriculture and climate change threats to agriculture. Plant microbe interactions form the basis of this review as evidence has shown that these interactions often exist to improve the health of plants. This is achieved by the production of important biochemicals and enzymes like indole acetic acid and amino cyclopropane-1-carboxylate deaminase while also actively protecting plants from pathogens including fungal pathogens. Research, therefore, has shown that these plant-growth promoting bacteria may be exploited and developed into biofertilisers. These biofertilisers are both economically and environmentally sustainable while improving soil quality and crop yield. The literature presented in this review is in context of the Namibian climate and soil profiles.

Central bearded dragons, Pogona vitticeps, are ectothermic heliotherms native to dry and arid regions and are often kept as exotic pets in colder less arid countries. They do however, often fall sick resulting in sudden death. This is now known to be caused by bacterial infections such as Listeria monocytogenes and Porphyromonas pogonae sp. This study therefore, aimed to identify microorganisms present in the buccal cavity of the central bearded dragon (P. vitticeps) in Namibia. In order to achieve this, oral swabs were taken from a bearded dragon found in a garden in Windhoek, Namibia and grown in nutrient agar. Colony morphology was described before Gram’s staining to differentiate the bacteria. The automated VITEK®2 system was used to identify the bacteria. On nutrient agar, opaque yellow circular colonies were observed after 24hrs incubation at 37°C. A gram-positive coccus shaped bacteria was observed. VITEK®2 analysis identified the bacteria as Micrococcus luteus. There has not been a study on the microbiota of the buccal cavity of the central bearded dragon in Namibia.

Detection of phytopathogens that are involved in causing disease symptoms in plants and crops is of prime importance as a key step in disease treatment and management. Ziziphus mucronata is a species endemic in temperate and tropical climates and used traditionally in the treatment of infectious diseases. The common bean (Phaseolus vulgaris) is a rich source of nutrients for the human diet. Just like most crops, it is not immune to fungal diseases and reports had been received of P. vulgaris showing signs on disease. The aim of this study was to isolate and characterize the fungal species associated with the disease symptoms in the Z. mucronata and P. vulgaris. Fungal species where isolated from surface-sterilised symptomatic bark of Z. muconata and fresh green bean pods. These where grown on petri dishes containing Potato Dextrose Agar and incubated at room temperature. Pure cultures where then obtained by transferring small segments of fungal growth to a new petri dish that contained PDA. During DNA extraction the pure cultures where first homogenized using liquid nitrogen and then the rest of the extraction carried out as stipulated in the Zymo extraction kit. The Nanodrop was used for quantifying the DNA and amplification of the conserved Internal Transcribed Spacer (ITS) region of Ribosomal RNA genes was carried out using ITS1 and ITS2. The PCR products were sequenced at Inqaba Biotech Industries in South Africa. The obtained sequences were then compared by alignment with known sequences in the Genbank using Basic Local Alignment Search Tool (BLAST). The BLAST searches were able to reveal the fungi isolated from the Z. mucronata as Fusarium penzigii and Fusarium dimerum while the fungi isolated from P. vulgaris shown to be Phoma destructiva, with 100 %, 95% and 100% sequence similarity respectively. The next step in this work is carry out Koch‘s postulates to determine which of this fungi is the causal agent of the observed diseases symptoms in order to start a targeted diseases management programme.

The occurrence of Salmonella is a global challenge in the public health and food production sectors. Our study investigated the prevalence, serovar and antimicrobial susceptibility of strains of Salmonella serovars isolated from animal feed (meat-and-bone and blood meal) samples from two commercial abattoirs in Namibia. A total of 650 samples (n = 650) were examined for the presence of Salmonella. Results showed that 10.9% (n = 71) were positive for Salmonella. Of the Salmonella serovars isolated, S. Chester was the most commonly isolated serovar (19.7%), followed by S. Schwarzengrund at 12.7%. From the Salmonella isolates, 19.7% (n = 14) were resistant to one or more of the antimicrobials (nalidixic acid, trimethoprim-sulfamethoxazole, sulfisoxa-zole, streptomycin and/or tetracycline), whereas 80.3% (n = 57) were susceptible to all 16 antimicrobials tested. Resistance to sulfisoxazole and the trimethroprim-suflamethoxazole combination were the most common. The resistant isolates belonged to ten different Salmonella serovars. The susceptibility of most of the Salmonella isolated to the antimicrobials tested indicates that anti-microbial resistance is not as common and extensive in Namibia as has been reported in many other countries. It also appears that there is a range of antimicrobials available that are effective in managing Salmonella infections in Namibia. However, there is some evidence that resistance is developing and this will need further monitoring to ensure it does not become a problem.