Search

A decline in common bean production and the ineffectiveness of synthetic chemical products in managing plant pathogens has led to exploiting Kenyan soda lakes as an alternative search for biocontrol agents. This study aimed to identify phylogenetically Bacillus spp. from Lake Magadi and their antagonistic activity against Rhizoctonia solani under in vitro and in vivo conditions. The 16 S ribosomal RNA (rRNA) subunit sequences of six bacterial strains isolated from Lake Magadi showed diversity similar to the Bacillus genus; Bacillus velezensis, Bacillus subtilis, and Bacillus pumilus. In vitro, antagonism showed varied mycelium inhibition rates of fungi in the coculture method. Enzymatic assays showed the varied ability of isolates to produce phosphatase, pectinase, chitinase, protease, indole‐3‐acetic acid (IAA), and hydrogen cyanide (HCD). The in vivo assay showed M09 (B. velezensis) with the lowest root mortality and incidence of postemergence wilt. Pre‐emergence wilt incidence was recorded as lowest in M10 (B. subtilis). Isolate M10 had the highest phenylalanine ammonia‐lyase (PAL) for defense enzymes, while polyphenol oxidase (PPO) and peroxidase were recorded as highest in M09. For the phenolic content, M10 recorded the highest phenolic content. In conclusion, Lake Magadi harbors Bacillus spp, which can be used as a potential biocontrol of R. solani. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the application of Decision Tree Classification (DTC) method for lithological mapping from multi-spectral satellite imagery. The area of investigation is the Lake Magadi in the East African Rift Valley in Kenya. The work involves the collection of rock and soil samples in the field, their analyses using reflectance and emittance spectroscopy, and the processing and interpretation of Advanced Spaceborne Thermal Emission and Reflection Radiometer data through the DTC method. The latter method is strictly non-parametric, flexible and simple which does not require assumptions regarding the distributions of the input data. It has been successfully used in a wide range of classification problems. The DTC method successfully mapped the chert and trachyte series rocks, including clay minerals and evaporites of the area with higher overall accuracy (86%). Higher classification accuracies of the developed decision tree suggest its ability to adapt to noise and nonlinear relations often observed on the surface materials in space-borne spectral image data without making assumptions on the distribution of input data. Moreover, the present work found the DTC method useful in mapping lithological variations in the vast rugged terrain accurately, which are inherently equipped with different sources of noises even when subjected to considerable radiance and atmospheric correction.

To meet the food and feed demands of the growing population, global food production needs to double by 2050. Climate change-induced challenges to food crops, especially soil salinization, remain a major threat to food production. We hypothesize that endophytic fungi isolated from salt-adapted host plants can confer salinity stress tolerance to salt-sensitive crops. Therefore, we isolated fungal endophytes from shrubs along the shores of saline alkaline Lake Magadi and evaluated their ability to induce salinity stress tolerance in tomato seeds and seedlings. Of 60 endophytic fungal isolates, 95% and 5% were from Ascomycetes and Basidiomycetes phyla, respectively. The highest number of isolates (48.3%) were from the roots. Amylase, protease and cellulase were produced by 25, 30 and 27 isolates, respectively; and 32 isolates solubilized phosphate. Only eight isolates grew at 1.5 M NaCl. Four fungal endophytes ( Cephalotrichum cylindricum, Fusarium equiseti, Fusarium falciforme and Aspergilus puniceus ) were tested under greenhouse conditions for their ability to induce salinity tolerance in tomato seedlings. All four endophytes successfully colonized tomato seedlings and grew in 1.5 M NaCl. The germination of endophyte-inoculated seeds was enhanced by 23%, whereas seedlings showed increased chlorophyll and biomass content and decreased hydrogen peroxide content under salinity stress, compared with controls. The results suggest that the the four isolates can potentially be used to mitigate salinity stress in tomato plants in salt-affected soils., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The research activities were approved by the Kenya Wildlife Service under research Authorization ref. KWS/BRM/5001 and NACOSTI research permit number NACOSTI/P/17/22929/14802., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Alcolapia grahami is a small cichlid fish that inhabits the scattered lagoons and sites of Lake Magadi (Kenya). Exceptional physiological, morphological, biochemical and behavioural adaptations allow the fish to tolerate the harsh environmental conditions that exist in the locations, the most extreme milieus occupied by a species of fish on Earth. The temperature of the water is inordinately high for a fish; large diurnal fluctuations in the levels of the partial pressure of oxygen occur, with acute hypoxia happening during the night and hyperoxia during the day; the salinity of the water is ~60% of that of seawater and; the pH may be as high as 11. Having an average adult body length of less than 6 cm and a body mass of ~5 g, the fish is very small in size. Here, body mass, body length, condition factors (CFs) and sex ratios (SRs) were determined on fish sampled from nine accessible isolated populations. Except for the Cement Water Holding Tanks (CWHT) population, where the female-to-male SR was 4:1, overall, the number of male fish surpassed the female ones by a ratio of ~2:1. The male fish were heavier and longer compared to the female ones. The relatively lower ambient temperature in the CWHT (32 °C) may explain the female dominated population and the effect future increase in temperature may have on sex distribution in the various populations of A. grahami. In fish from the Fish Spring Lagoons B and D, the CFs were greater in the male fish relative to the female ones. Exhibiting poor-to-fair body states, the CFs of the different populations of A. grahami, that ranged from 1.1. to 1.8, were among the lowest that have been reported in fish living under natural setting. The skewed SRs and the markedly low CFs of A. grahami reported here may be ascribed to the harsh (stressful) environmental conditions the fish contends with. The values may signal prospective demise of the fish. Conservation measures are urgently needed to protect a very rare fish. [ABSTRACT FROM AUTHOR]

Mineral vesicles and chemical gardens are self-organized biomimetic structures that form via abiotic mineral precipitation. These membranous structures are known to catalyze prebiotic reactions but the extreme conditions required for their synthesis has cast doubts on their formation in nature. Apart from model solutions, these structures have been shown to form in serpentinization-driven natural silica-rich water and by fluid-rock interaction of model alkaline solutions with granites. Here, for the first time, we demonstrate that self-assembled hollow mineral vesicles and gardens can be synthesized in natural carbonate-rich soda lake water. We have synthesized these structures by a) pouring saturated metal salt solutions, and b) by immersing metal salt pellets in brines collected from Lake Magadi (Kenya). The resulting structures are analyzed by using SEM coupled with EDX analysis, Raman spectroscopy, and powder X-ray diffraction. Our results suggest that mineral self-assembly could have been a common phenomenon in soda oceans of early Earth and Earth-like planets and moons. The composition of the obtained vesicles and gardens confirms the recent observation that carbonate minerals in soda lakes sequestrate Ca, thus leaving phosphate behind in solution available for biochemical reactions. Our results strengthens the proposal that alkaline brines could be ideal sites for “one-pot” synthesis of prebiotic organic compounds and the origin of life.

Copyright of Parasite (1252607X) is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Evidence for Quaternary climate change in East Africa has been derived from outcrops on land and lake cores and from marine dust, leaf wax, and pollen records. These data have previously been used to evaluate the impact of climate change on hominin evolution, but correlations have proved to be difficult, given poor data continuity and the great distances between marine cores and terrestrial basins where fossil evidence is located. Here, we present continental coring evidence for progressive aridification since about 575 thousand years before present (ka), based on Lake Magadi (Kenya) sediments. This long-term drying trend was interrupted by many wet-dry cycles, with the greatest variability developing during times of high eccentricity-modulated precession. Intense aridification apparent in the Magadi record took place between 525 and 400 ka, with relatively persistent arid conditions after 350 ka and through to the present. Arid conditions in the Magadi Basin coincide with the Mid-Brunhes Event and overlap with mammalian extinctions in the South Kenya Rift between 500 and 400 ka. The 525 to 400 ka arid phase developed in the South Kenya Rift between the period when the last Acheulean tools are reported (at about 500 ka) and before the appearance of Middle Stone Age artifacts (by about 320 ka). Our data suggest that increasing Middle- to Late-Pleistocene aridification and environmental variability may have been drivers in the physical and cultural evolution of Homo sapiens in East Africa. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the application of Decision Tree Classification (DTC) method for lithological mapping from multi-spectral satellite imagery. The area of investigation is the Lake Magadi in the East African Rift Valley in Kenya. The work involves the collection of rock and soil samples in the field, their analyses using reflectance and emittance spectroscopy, and the processing and interpretation of Advanced Spaceborne Thermal Emission and Reflection Radiometer data through the DTC method. The latter method is strictly non-parametric, flexible and simple which does not require assumptions regarding the distributions of the input data. It has been successfully used in a wide range of classification problems. The DTC method successfully mapped the chert and trachyte series rocks, including clay minerals and evaporites of the area with higher overall accuracy (86%). Higher classification accuracies of the developed decision tree suggest its ability to adapt to noise and nonlinear relations often observed on the surface materials in space-borne spectral image data without making assumptions on the distribution of input data. Moreover, the present work found the DTC method useful in mapping lithological variations in the vast rugged terrain accurately, which are inherently equipped with different sources of noises even when subjected to considerable radiance and atmospheric correction. [ABSTRACT FROM AUTHOR]

Fungi able to survive under the extreme environment of soda lakes remain poorly studied. This paper presents data on the diversity and ecophysiology of filamentous fungi inhabiting one of the most alkaline habitats of the Earth: Lake Magadi, where pH values may exceed 11-12. The lake is home to a large number of prokaryotes, which form complex communities with algae and some other eukaryotes. In this study, 22 species of filamentous fungi isolated from soil samples collected on the coastline of Lake Magadi have been characterized using a systematic approach, which includes selective isolation, an analysis of morphological traits, molecular-genetic analysis, growth experiments to determine pH and temperature preferences, and an analysis of the dependence on NaCl concentrations. According to the results, alkaline soil from the Lake Magadi coastline is colonized by fungi with differing types of adaptation to high pH values. Alkaliphilic and alkalitolerant fungi belong to different families of Ascomycetes, mainly to Plectosphaerellaceae, as well as to Onygenaceae, Trihocomaceae, and Pleosporaceae. Sodiomyces tronii and S. magadii are new obligate alkaliphilic species within the earlier monotypic genus Sodiomyces (Plectosphaerellaceae). According to the growth experiments, obligate alkaliphilic isolates demonstrate thermo- and halotolerant properties. The problems of adaptation to the external pH, possible substrate preferences, and association of alkaliphilic fungi with other organisms are discussed. [ABSTRACT FROM AUTHOR]

Background: Lake Magadi and little Magadi are hypersaline, alkaline lakes situated in the southern part of Kenyan Rift Valley. Solutes are supplied mainly by a series of alkaline hot springs with temperatures as high as 86 °C. Previous culture-dependent and culture-independent studies have revealed diverse groups of microorganisms thriving under these conditions. Previous culture independent studies were based on the analysis of 16S rDNA but were done on less saline lakes. For the first time, this study combined illumina sequencing and analysis of amplicons of both total community rDNA and 16S rRNA cDNA to determine the diversity and community structure of bacteria and archaea within 3 hot springs of L. Magadi and little Magadi. Methods: Water, wet sediments and microbial mats were collected from springs in the main lake at a temperature of 45.1 °C and from Little Magadi "Nasikie eng'ida" (temperature of 81 °C and 83.6 °C). Total community DNA and RNA were extracted from samples using phenol-chloroform and Trizol RNA extraction protocols respectively. The 16S rRNA gene variable region (V4 - V7) of the extracted DNA and RNA were amplified and library construction performed following Illumina sequencing protocol. Sequences were analyzed done using QIIME while calculation of Bray-Curtis dissimilarities between datasets, hierarchical clustering, Non Metric Dimensional Scaling (NMDS) redundancy analysis (RDA) and diversity indices were carried out using the R programming language and the Vegan package. Results: Three thousand four hundred twenty-six and one thousand nine hundred thirteen OTUs were recovered from 16S rDNA and 16S rRNA cDNA respectively. Uncultured diversity accounted for 89.35 % 16S rDNA and 87.61 % 16S rRNA cDNA reads. The most abundant phyla in both the 16S rDNA and 16S rRNA cDNA datasets included: Proteobacteria (8.33-50 %), Firmicutes 3.52-28.92 %, Bacteroidetes (3.45-26.44 %), Actinobacteria (0.98-28.57 %) and Euryarchaeota (3.55-34.48 %) in all samples. NMDS analyses of taxonomic composition clustered the taxa into three groups according to sample types (i.e. wet sediments, mats and water samples) with evident overlap of clusters between wet sediments and microbial mats from the three sample types in both DNA and cDNA datasets. The hot spring (45.1 °C) contained less diverse populations compared to those in Little Magadi (81-83 °C). Conclusion: There were significant differences in microbial community structure at 95 % level of confidence for both total diversity (P value, 0.009) based on 16S rDNA analysis and active microbial diversity (P value, 0.01) based on 16S rRNA cDNA analysis, within the three hot springs. Differences in microbial composition and structure were observed as a function of sample type and temperature, with wet sediments harboring the highest diversity. [ABSTRACT FROM AUTHOR]

Studying recent adaptive radiations in isolated insular systems avoids complicating causal events and thus may offer clearer insight into mechanisms generating biological diversity. Here, we investigate evolutionary relationships and genomic differentiation within the recent radiation of Alcolapia cichlid fish that exhibit extensive phenotypic diversification, and which are confined to the extreme soda lakes Magadi and Natron in East Africa. We generated an extensive RAD data set of 96 individuals from multiple sampling sites and found evidence for genetic admixture between species within Lake Natron, with the highest levels of admixture between sympatric populations of the most recently diverged species. Despite considerable environmental separation, populations within Lake Natron do not exhibit isolation by distance, indicating panmixia within the lake, although individuals within lineages clustered by population in phylogenomic analysis. Our results indicate exceptionally low genetic differentiation across the radiation despite considerable phenotypic trophic variation, supporting previous findings from smaller data sets; however, with the increased power of densely sampled SNPs, we identify genomic peaks of differentiation ( FST outliers) between Alcolapia species. While evidence of ongoing gene flow and interspecies hybridization in certain populations suggests that Alcolapia species are incompletely reproductively isolated, the identification of outlier SNPs under diversifying selection indicates the radiation is undergoing adaptive divergence. [ABSTRACT FROM AUTHOR]

The occurrence of Picocystis salinarunm in saline inland waters of East Africa was investigated using a polyphasic approach of small-subunit (SSU) rDNA phylogeny and light microscope observations. Recent studies have found that Picocystis occasionally replaces the dominant cyanobacterium (Arthrospira fusiformis),which is the main food resource of Lesser Flamingos in soda lakes of Bogoria and Nakuru This article discusses the consequences of a high abundance (maximum cell numbers of> 3 billion cells l-1) of Picocystis on food chains of African salihe waters. During the study, we found a new morphotype of Picocystis characterized by larger cell sizes and absence of lobes in hot springs near Lake Magadi. SSU rRNA genes of Picocystis strains and uncultured field clones collected from Lake Nakuru were subjected to phylogenetic analyses together with other picoplankton from field and culture samples from saline marine or freshwater Picocystis salinarum from saline inland waters represents a link between marine and freshwater habitats from both an ecological and a phylogenetic point of view and is therefore of great interest. [ABSTRACT FROM AUTHOR]

Abstract: Southern Kenya Rift has been known as a region of high geodynamic activity expressed by recent volcanism, geothermal activity and high rate of seismicity. The active faults that host these activities have not been investigated to determine their subsurface geometry, faulting intensity and constituents (fluids, sediments) for proper characterization of tectonic rift extension. Two different models of extension direction (E–W to ESE–WNW and NW–SE) have been proposed. However, they were based on limited field data and lacked subsurface investigations. In this research, we delineated active fault zones from ASTER image draped on ASTER DEM, together with relocated earthquakes. Subsequently, we combined field geologic mapping, electrical resistivity, ground magnetic traverses and aeromagnetic data to investigate the subsurface character of the active faults. Our results from structural studies identified four fault sets of different age and deformational styles, namely: normal N–S; dextral NW–SE; strike slip ENE–WSW; and sinistral NE–SW. The previous studies did not recognize the existence of the sinistral oblique slip NE–SW trending faults which were created under an E–W extension to counterbalance the NW–SE faults. The E–W extension has also been confirmed from focal mechanism solutions of the swarm earthquakes, which are located where all the four fault sets intersect. Our findings therefore, bridge the existing gap in opinion on neo-tectonic extension of the rift suggested by the earlier authors. Our results from resistivity survey show that the southern faults are in filled with fluid (0.05 and 0.2Ωm), whereas fault zones to the north contain high resistivity (55–75Ωm) material. The ground magnetic survey results have revealed faulting activity within active fault zones that do not contain fluids. In addition, the 2D inversion of the four aero-magnetic profiles (209km long) revealed: major vertical to sub vertical faults (dipping 75–85° east or west); an uplifted, heavily fractured and deformed basin to the north (highly disturbed magnetic signatures) characteristic of on going active rifting; and a refined architecture of the asymmetry graben to the south with an intrarift horst, whose western graben is 4km deep and eastern graben is much deeper (9km), with a zone of significant break in magnetic signatures at that depth, interpreted as source of the hot springs south of Lake Magadi (a location confirmed near surface by ground magnetic and resistivity data sets). The magnetic sources to the north are shallow at 15km depth compared to 22km to the south. The loss of magnetism to the north is probably due to increased heat as a result of magmatic intrusion supporting active rifting model. Conclusively, the integrated approach employed in this research confirms that fault system delineated to the north is actively deforming under E–W normal extension and is a potential earthquake source probably related to magmatic intrusion, while the presence of fluids within the south fault zone reduce intensity of faulting activity and explains lack of earthquakes in a continental rift setting. [Copyright &y& Elsevier]

Mineral vesicles and chemical gardens are self-organized biomimetic structures that form via abiotic mineral precipitation. These membranous structures are known to catalyze prebiotic reactions but the extreme conditions required for their synthesis has cast doubts on their formation in nature. Apart from model solutions, these structures have been shown to form in serpentinization-driven natural silica-rich water and by fluid-rock interaction of model alkaline solutions with granites. Here, for the first time, we demonstrate that self-assembled hollow mineral vesicles and gardens can be synthesized in natural carbonate-rich soda lake water. We have synthesized these structures by a) pouring saturated metal salt solutions, and b) by immersing metal salt pellets in brines collected from Lake Magadi (Kenya). The resulting structures are analyzed by using SEM coupled with EDX analysis, Raman spectroscopy, and powder X-ray diffraction. Our results suggest that mineral self-assembly could have been a common phenomenon in soda oceans of early Earth and Earth-like planets and moons. The composition of the obtained vesicles and gardens confirms the recent observation that carbonate minerals in soda lakes sequestrate Ca, thus leaving phosphate behind in solution available for biochemical reactions. Our results strengthens the proposal that alkaline brines could be ideal sites for "one-pot" synthesis of prebiotic organic compounds and the origin of life. [ABSTRACT FROM AUTHOR]