Physical and Chemical Characteristics of Five Hot Springs in Eritrea

Eritrea has a number of hot springs whose physicochemical characteristics are not documented. This study examined the thermal and chemical features of five hot springs located in the eastern escarpment of Eritrea. Field data and water samples were collected from five hot springs namely; Akwar and Maiwooi near Gahtelai, Garbanabra and Gelti near Irafayle at the Gulf of Zula and Elegedi in Alid volcanic center. The water temperatures at source varied from 49.5°C to 100°C while pH levels ranged from 6.97 to 7.54. Elegedi had significantly higher temperature (p < 0.05) than the other four hot springs. Strong correlation was observed between electrical conductivity (EC), total dissolved solid (TDS), salinity, sodium, potassium, calcium and chloride (R2 > 0.9) as well as between temperature and sulphate levels (R2 = 0.96). Evident clustering was noted at p < 0.05, using Non-metric multidimensional scaling (NMDS), between the three locations of the hot springs. Akwar and Maiwooi, situated close to each other, clustered together, Garbanabra and Gelti, which were characterized by higher salinity levels, formed a separate cluster. Elegedi, characterized by high temperature (100°C), sulphate (979.7 mg/l) and NH4+ (196.33 mg/l) levels, clustered separately. Akwar and Maiwooi had high bicarbonate (345 mg/l and 393 mg/l) and fluoride (8.20 mg/l and 6.48 mg/l) levels which are above WHO limits. Electrical conductivity (23,133 mS/cm), total dissolved solid (15,552 mg/l), sodium (3,800 mg/l), potassium (198 mg/l), calcium (1,653 mg/l) and chloride (5,946 mg/l) levels in Garbanabra and Gelti hot springs exceeded WHO limits. Bromine (74.8 mg/l in Garbanabra and 45.2 mg/l in Gelti) and boron (2.21 mg/l in Garbanabra and 1.55 mg/l in Gelti) levels were also above standard limits set for potable water. Maiwooi (1.20) and Elegedi (1.10) were depositional while Akwar water (-0.71) was slightly corrosive. The corrosive nature of the water sample from Akwar, is a public health concern. The waters from the five Eritrean hot springs are thus not fit for human consumption. In addition, the use of thermal spring water for recreational purposes should be closely monitored. Keywords: key words, hot springs, physicochemical, Eritre

Dicamba growth regulator promotes genotype independent somatic embryogenesis from immature zygotic embryos of tropical maize inbred lines

Maize is one of the most important cereal crops in Sub-Saharan Africa and an important source of energy for humans. However, the difference in the dedifferentiation frequency of immature embryos among various genotypes indicates that callus induction and genetic transformation is dependent on the genotype. This phenomenon is an impediment in the fundamental process of improving tropical maize germplasm especially through genetic engineering. Here, five tropical maize (Zea mays L.) genotypes, CML 216, CML 144, A 04, E 04 and TL 21, were evaluated for callus induction on MS medium supplemented with the growth regulator dicamba. Embryogenic and non embryogenic callus induction was independent of genotype when young immature embryos, 12 days after pollination (DAP) were used for tissue culture in combination with dicamba. The optimal concentration of dicamba for induction of embryogenic callus in all the genotypes was 3 mg/L, which was also the concentration at which non embryogenic callus formation was lowest. The frequency of embryogenic callus induction ranged from 35% to 79% among the five genotypes and somatic embryos regenerated R0 shoots that produced normal R1 progenies. This regeneration method is expected to facilitate the development of a more efficient genotype independent Agrobacterium- mediated transformation system for tropical inbred lines

Genetic Improvement of African Maize towards Drought Tolerance: A Review

Africa supports a population of over 1 billion people with over half of them depending on maize for food and feed either directly or indirectly.  Maize in Africa is affected by many stresses, both biotic and abiotic which significantly reduce yields and eventually lead to poor production.  Due to the high demand for maize in the region, different improvement strategies have been employed in an effort to improve production.  These include conventional breeding, molecular breeding, high throughput phenotyping techniques and remote sensing-based techniques.  Conventional breeding techniques such as open pollination have been used to develop drought avoiding maize varieties like the Kito open pollinated variety (OPV) of Tanzania and Guto OPV of Ethiopia.  A combination of conventional breeding and molecular biology techniques has led to improved breeding strategies like the Marker Assisted Back Crossing (MABC) and Marker Assisted Recurrent Selection (MARS).  These techniques have been used to improve drought tolerance in existing inbred maize lines like the CML 247 and CML 176.  Through genetic engineering, different genes including C4-PEPC, NPK1, betA, ZmNF-YB2, cspB, ZmPLC1 and TsVP have been cloned in maize.  Transgenic maize crops expressing these genes have shown increased tolerance to drought stress.  Although there is substantial progress towards developing drought tolerant maize, many African farmers are yet to benefit from this technology.  This is due to lack of an enabling policy framework as well as a limited financial investment in biotechnology research. Keywords: Maize, Drought tolerance, Genetic engineering; Biotechnology; Transgenic crop

Genetic Transformation of Sweet Potato for Improved Tolerance to Stress: A Review

The sweet potato (Ipomoea batatas Lam) is a major staple food in many parts of the world. Sweet potato leaves and tubers are consumed as food and livestock feed. Biotic and abiotic stresses affect yield leading to a reduction in production. This review analyzes factors limiting sweet potato production and the progress made towards stress tolerance using genetic transformation. Genetic transformation could enhance yield, nutritional value and tolerance to stress. Transgenic sweet potatoes tolerant to biotic and abiotic stress, improved nutritional value and higher yields have been developed. Sweet potato expressing the endotoxin cry8Db, cry7A1 and cry3Ca genes showed lower sweet potato weevil infestation than non-transformed lines. Transgenic cultivar ‘Xushu18’ expressing the oryzacystatin-1 (OC1) gene showed enhanced resistance to sweet potato stem nematodes. Sweet potato line ‘Chikei 682-11’ expressing the coat protein (CP) exhibited resistance to the sweet potato feathery mottle virus (SPFMV). Transgenics expressing the rice cysteine inhibitor gene oryzacystatin-1 (OC1) also exhibited resistance to the SPFMV. Transgenic cultivar ‘Kokei’ expressing the spermidine synthetase gene FSPD1 had higher levels of spermine in the leaves and roots, and displayed enhanced tolerance to drought and salt stress. ‘Shangshu’ variety expressing the IbMas has shown enhanced tolerance to salt stress. Transgenic ‘Lixixiang’ expressing IbMIPSI showed an up-regulation of metabolites involved in stress response to drought, salinity and nematode infestation. Transgenic ‘Yulmi’ sweet potato transformed with copper/zinc superoxide dismutase (CuZnSOD) gene showed an enhanced tolerance to methyl viologen induced oxidative and chilling stress. Similarly, transformation of cultivar ‘Sushu-2’ with betaine aldehyde dehydrogenase (BADH) gene resulted in transgenics tolerant to salt, chilling and oxidative stress. Sweet potato varieties ‘Kokei14’ and ‘Yulmi’ transformed with the bar gene were shown to be tolerant to application of the herbicide Basta. The development of stress tolerant varieties will immensely increase the area under sweet potato production and eventually promote the adoption of sweet potato as a commercial crop. Sweet potato research and breeding for stress tolerance still faces technical and socio-political hurdles. Despite these challenges, genetic transformation remains a viable method with immense potential for the improvement of sweet potato. Key words: Sweet Potato (Ipomoea batatas Lam), Stress, Genetic Transformation, Transgeni

The Isolation, Screening, and Characterization of Polyhydroxyalkanoate-Producing Bacteria from Hypersaline Lakes in Kenya

Extremophilic microorganisms such as those that thrive in high-salt and high-alkaline environments are promising candidates for the recovery of useful biomaterials including polyhydroxyalkanoates (PHAs). PHAs are ideal alternatives to synthetic plastics because they are biodegradable, biocompatible, and environmentally friendly. This work was aimed at conducting a bioprospection of bacteria isolated from hypersaline-alkaliphilic lakes in Kenya for the potential production of PHAs. In the present study, 218 isolates were screened by Sudan Black B and Nile Red A staining. Of these isolates, 31 were positive for PHA production and were characterized using morphological, biochemical, and molecular methods. Through 16S rRNA sequencing, we found that the isolates belonged to the genera Arthrobacter spp., Bacillus spp., Exiguobacterium spp., Halomonas spp., Paracoccus spp., and Rhodobaca spp. Preliminary experiments revealed that Bacillus sp. JSM-1684023 isolated from Lake Magadi had the highest PHA accumulation ability, with an initial biomass-to-PHA conversion rate of 19.14% on a 2% glucose substrate. Under optimized fermentation conditions, MO22 had a maximum PHA concentration of 0.516 g/L from 1.99 g/L of cell dry weight and 25.9% PHA conversion, equivalent to a PHA yield of 0.02 g/g of biomass. The optimal PHA production media had an initial pH of 9.0, temperature of 35 °C, salinity of 3%, and an incubation period of 48 h with 2.5% sucrose and 0.1% peptone as carbon and nitrogen sources, respectively. This study suggests that bacteria isolated from hypersaline and alkaliphilic tropical lakes are promising candidates for the production of polyhydroxyalkanoates

Evaluation of prokaryotic diversity of five hot springs in Eritrea

Abstract Background Total community rDNA was used to determine the diversity of bacteria and archaea from water, wet sediment and microbial mats samples of hot springs in the Eastern lowlands of Eritrea. The temperatures of the springs range from 49.5 °C to 100 °C while pH levels varied from 6.97 to 7.54. Akwar and Maiwooi have high carbonate levels. The springs near the seashore, Garbanabra and Gelti, are more saline with higher levels of sodium and chlorides. Elegedi, situated in the Alid volcanic area, has the highest temperature, iron and sulfate concentrations. Results The five hot springs shared 901 of 4371 OTUs recovered while the three sample types (water, wet sediment and microbial mats) also shared 1429 OTUs. The Chao1 OTU estimate in water sample was significantly higher than the wet sediment and microbial mat samples. As indicated by NMDS, the community samples at genus level showed location specific clustering. Certain genera correlated with temperature, sodium, carbonate, iron, sulfate and ammonium levels in water. The abundant phyla included Proteobacteria (6.2–82.3%), Firmicutes (1.6–63.5%), Deinococcus-Thermus (0.0–19.2%), Planctomycetes (0.0–11.8%), Aquificae (0.0–9.9%), Chlorobi (0.0–22.3%) and Bacteroidetes (2.7–8.4%). Conclusion There were significant differences in microbial community structure within the five locations and sample types at OTU level. The occurence of Aquificae, Deinococcus-Thermus, some Cyanobacteria and Crenarchaeota were highly dependent on temperature. The Halobacterium, unclassified Thaumarchaeota, Actinobacteria and Cyanobacteria showed significant correlation with salinity occurring abundantly in Garbanabra and Gelti. Firmicutes and unclassified Rhodocylaceae were higher in the microbial mat samples, while Archaea were prominent in the wet sediment samples