DSpace Repository :: Browsing by Author "Dadheech, Pawan K."

Browsing by Author "Dadheech, Pawan K."

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Cyanobacterial diversity in the hot spring, pelagic and benthic habitats of a tropical soda lake
(2013-08) Dadheech, Pawan K.; Glockner, G.; Casper, P.; Kotut, Kiplagat; Mazzoni, C.J.; Mbedi, S.; Krienitz, L.
Hot springs and saline-alkaline lakes of East Africa are extreme habitats regarding temperature, or salinity and pH, respectively. This study examines whether divergent habitats of Lake Bogoria, Kenya, impacts cyanobacterial community structure. Samples from the hot springs, pelagic zone and sediment were analysed by light microscopy, multilocus 454-amplicons sequencing and metagenomics to compare the cyanobacterial diversity. Most of the phylogenetic lineages of Cyanobacteria occurred exclusively in the Bogoria hot springs suggesting a high degree of endemism. The prevalent phylotypes were mainly members of the Oscillatoriales (Leptolyngbya, Spirulina, Oscillatoria-like and Planktothricoides). The Chroococcales were represented by different clades of Synechococcus but not a single phylotype clustered with any of the lineages described earlier from different continents. In contrast, we found that the pelagic zone and the sediments were inhabited by only a few taxa, dominated by Arthrospira and Anabaenopsis. Arthrospira, the main food base of Lesser Flamingo, was detected in all three habitats by amplicons pyrosequencing, indicating its resilience and key role as a primary producer. Despite the close connection between the three habitats studied, the cyanobacterial communities in the hot springs and lake differed considerably, suggesting that they are unable to adapt to the extreme conditions of the neighbouring habitat.
Desertifilum fontinale sp. nov. (Oscillatoriales, Cyanobacteria) from a warm spring in East Africa, based on conventional and molecular studies
(2014) Dadheech, Pawan K.; Mahmoud, Huda; Kotut, Kiplagat; Krienitz, L.
Desertifilum is a filamentous cyanobacterium of crusts and biofilms, recently described from the extreme hot and dry Thar Desert in north–western India. A new species was isolated from a warm spring near Lake Bogoria, Kenya and was characterised by light and electron microscopy and phylogenetically using the 16S rRNA gene, beta and alpha subunits including intergenic spacer (cpcBA–IGS) and 16S–23S internal transcribed spacer (ITS). The aquatic habitat of the new material from Kenya revealed a wider distribution of members of this genus. The new taxon was found to be closest to Desertifilum tharense (Oscillatoriales). The separation of the new species described here as D. fontinale sp. nov., using conventional and molecular traits, was based on differences in phenotypic features, 16S–23S ITS sequence and habitat.
Food algae for Lesser Flamingos: a stocktaking
(Springer, 2016-07) Krienitz, Lothar; Krienitz, Doris; Dadheech, Pawan K.; Hübener, Thomas; Kotut, Kiplagat; Luo, Wei; Teubner, Katrin; Versfeld, Wilferd D.
Lesser Flamingo, the flagship species of saline wetlands of Africa and India, is a specialised feeder subsisting on microscopic cyanobacteria and algae. To establish the relationship between flamingo occurrence and food algal abundance and quality, an extensive microphyte survey in more than 150 sampling trips to seven countries over a 15-years period (2001–2015) was carried out. The 44 habitat sites included the core soda lakes in eastern Africa (Bogoria, Nakuru, Elmentaita, Oloidien), where the highest numbers of flamingos were observed, and five breeding sites in eastern and southern Africa as well as in north-western India. A reference describing the diversity of microphytes was established including members of three orders of cyanobacteria and nine orders of eukaryotic algae that potentially could act as food source for Lesser Flamingos. Preferred food organisms consisted of filamentous cyanobacteria, mainly Arthrospira, as well as benthic diatoms. Further investigation on the suitability of other microphytes as alternative flamingo diet revealed the food potential of chlorophytes and euglenophytes. This paper discusses a phycological perspective in the feeding ecology of Lesser Flamingos. The survey findings can assist scientists and conservationists in evaluating the potential of wetlands to support flocks of this endangered bird.
Haloleptolyngbya alcalis gen. et sp. nov., a new filamentous cyanobacterium from the soda lake Nakuru, Kenya
(Springer, 2012) Dadheech, Pawan K.; Mahmoud, Huda; Kotut, Kiplagat; Krienitz, L.
The food web of the saline-alkaline Lake Nakuru is dominated by the cyanobacterium Arthrospira fusiformis as the primary producer and a huge population of Lesser Flamingos as direct consumers. However, the dense blooms of Arthrospira are not stable, and collapse irregularly and unpredictably. During such periods they are replaced by other algae or cyanobacteria. The wide fluctuation in the cyanobacterial and algal populations of Lake Nakuru has a great influence on food availability for Lesser Flamingos, and is therefore of high ecological importance. To support the descriptive work on these phenomena, we describe here a new cyanobacterial taxon from this soda lake: Haloleptolyngbya alcalis Dadheech, Mahmoud, Kotut et Krienitz gen. et sp. nov. The study was based on multilocus molecular analyses of 16S rRNA gene, 16S-23S internal transcribed spacer, partial sequences of beta and alpha subunits including intergenic spacer (cpcBA-IGS) of phycocyanin operon, phenotypic features using light microscopy, scanning electron microscopy, transmission electron microscopy, and ecology. The new taxon established a separate lineage within the family of Peudanabaenaceae (Oscillatoriales).
Mass developments of a small sized ecotype of Arthrospira fusiformis in Lake Oloidien, Kenya, a new feeding ground for Lesser Flamingos in East Africa
(2013) Krienitz, L.; Dadheech, Pawan K.; Kotut, Kiplagat
The Lesser Flamingos constantly commute between the soda lakes of East Africa in search of food. Their preferred food, the cyanobacterium Arthrospira fusiformis, usually establishes dense populations in saline–alkaline habitats. However, the algal food resources are not stable and crash unexpectedly from time to time. Hence any site that provides food in suitable quality and quantity makes a valuable contribution to the survival of these nearly endangered birds. This paper reports on the development of a new feeding ground for the Lesser Flamingos; Lake Oloidien, a former bay of the freshwater lake Naivasha. Phytoplankton succession and biomass, salinity and flamingo numbers were analysed over the period 2001–2013. As a result of a progressive increase in salinity to values of between 3 and 6 ppt, Oloidien has since 2006 hosted dense blooms of a small sized ecotype of A. fusiformis. Molecular phylogenetic analyses using the 16S–23S internal transcribed spacer (ITS) and partial sequences of the beta and alpha subunits including intergenic spacer (cpcBA–IGS) of the phycocyanin operon confirmed that a field clone and one isolated strain of Arthrospira from Lake Oloidien was similar to the strains in other soda lakes of Kenya. PCR–based results confirmed the non–toxic character of the isolated Arthrospira strain. The biomass of Arthrospira in the whole lake ranged from 236 to 301 t dry weight in the phase when more than 100,000 flamingos were present (2006–2012). Based on the biomass of Arthrospira present, the carrying capacity of Lake Oloidien was calculated to be 150,000–250,000 Lesser Flamingos. In the phase of low flamingo numbers (2013), the biomass of Arthrospira in the lake rose to a value of 922 t.
Mass developments of the cyanobacteria Anabaenopsis and Cyanospira (Nostocales) in the soda lakes of Kenya: ecological and systematic implications
(2013) Krienitz, L.; Dadheech, Pawan K.; Kotut, Kiplagat
The food web of the saline–alkaline lakes of East Africa is characterised by a unique interaction between the Lesser Flamingos as consumer birds and the cyanobacterium Arthrospira fusiformis as the primary producer. However, this interaction is disturbed frequently by alterations of the phytoplankton community. During the period 2001–2012, species of the cyanobacteria Anabaenopsis and Cyanospira were observed in four soda lakes of the African Rift Valley and compared to the entire phytoplankton biomass and composition. Their morphology was highly variable. Each species preferred a distinct range of salinity: C. capsulata 30–40 ppt, C. rippkae 25–35 ppt, A. arnoldii and A. abijatae 10–30 ppt, and A. elenkinii 0–15 ppt. Occasional dominance of Anabaenopsis and Cyanospira in the lakes investigated shows that members of these genera are serious competitors of A. fusiformis, the main food for Lesser Flamingos. Furthermore, mass developments of C. capsulata adversely affected food uptake by the flamingos at Lake Bogoria because they formed mucilaginous colonies that clogged the food filter system. From field samples of the three lakes, uncultured Anabaenopsis and Cyanospira spp. clones were obtained and subjected to phylogenetic analyses. The 16S rRNA gene sequencing data put into doubt the differentiation of Anabaenopsis and Cyanospira into separate genera as recently suggested.
Molecular detection of uncultured cyanobacteria and aminotransferase domains for cyanotoxin production in sediments of different Kenyan lakes
(Blackwell Publishing Ltd, 2009-04-15) Dadheech, Pawan K.; Krienitz, L.; Kotut, Kiplagat; Ballot, A.; Casper, P.
PCR-based denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments was used to identify the cyanobacterial phylotypes in sediments and plankton of saline–alkaline and freshwater lakes of Kenya. The detection of the aminotransferase domain located on modules mcyE and ndaF using specific molecular markers confirmed the presence of potential toxin-producing cyanobacteria. The eight nucleotide sequences obtained from DGGE bands were placed in three divergent cyanobacterial clusters. Five nucleotide sequences were close to members of the genera Anabaenopsis and Umezakia (Nostocales), two sequences fell in the cluster with Arthrospira sp. (Oscillatoriales) and one sequence was related to Chroococcidiopsis sp. (Pleurocapsales). The presence of the latter taxon was demonstrated de novo in the investigated lakes. All nine attained nucleotide sequences of the aminotransferase region belonged to the mcyE module. Five sequences of the aminotransferase domain were included in the cluster having the nucleotide sequence of Anabaena sp. but showed a separate lineage. Other four aminotransferases were placed in the cluster represented by nucleotide sequence of Microcystis aeruginosa. To our knowledge, this is the first report on molecular detection of cyanobacterial phylotypes in sediments of African lakes and aminotransferase domains for cyanotoxin production from sediment samples in general.
Phylogenetic relationship and divergence among planktonic strains of Arthrospira (Oscillatoriales, Cyanobacteria) of African, Asian and American origin deduced by 16S–23S ITS and phycocyanin operon sequences
(2010-07) Dadheech, Pawan K.; Ballot, A.; Casper, P.; Kotut, Kiplagat; Novelo, E.; Lemma, B.; Proschold, T.; Krienitz, L.
Arthrospira comprises multicellular, cylindrical, usually screwlike coiled trichomes and is cultivated commercially. In this study, 33 new strains of Arthrospira isolated from plankton samples collected in Mexico, East Africa and India were investigated and compared with 53 strains or samples of earlier considerations. The study included observations of morphological features and molecular phylogenetic analyses on the basis of nucleotide sequences of internal transcribed spacer (ITS) between 16S rRNA and 23S rRNA genes and partial sequences of beta and alpha subunits including intergenic spacer (cpcBA-IGS) of phycocyanin operon. Morphological traits of Arthrospira such as trichome width, type of coiling and apical cell were not always consistent in culture conditions. It was revealed that Arthrospira phylogeny on the basis of cpcBA-IGS locus was broadly comparable with the ITS region as both phylogenetic trees derived from nucleotide sequences could be divided into two main clusters. Cluster I comprised sequences from American strains mainly, whereas cluster II contained the sequences of the strains originating from Africa and Asia chiefly. Both genetic regions of the strains investigated in the present study coincidently showed a significant sequence divergence among Arthrospira strains from East Africa, India and Mexico indicating possible distinct evolutionary lineages.
The rise of potentially toxin producing cyanobacteria in Lake Naivasha, Great African Rift Valley, Kenya
(Elsevier, 2013-07) Krienitz, L.; Dadheech, Pawan K.; Jutta, Fastner; Kotut, Kiplagat
Lake Naivasha, an important inland water ecosystem and a crucial freshwater resource in the Great African Rift Valley, has displayed clear signals of degradation in recent decades. We studied the phytoplankton composition and biomass levels in the period 2001–2013 and noted a progressive increase in the occurrence of potentially toxic cyanobacteria. Analyses for the presence of cyanotoxins such as microcystins (MC), cylindrospermopsin (CYN) and anatoxin-a (ATX-a) were carried out on samples collected in 2008–2013. Among the cyanotoxins tested, low concentrations of MC were detected in the lake. This is the first record of the occurrence of MC in Lake Naivasha. For the first time, molecular phylogenetic investigations of field clones of cyanobacteria from Lake Naivasha were carried out to establish the taxa of the dominant species. Amplification of the aminotrasferase (AMT) domain responsible for cyanotoxin production confirmed the presence of the mcyE gene belonging to the microcystin synthesis gene cluster in field samples containing Microcystis and Planktothrix species. These findings suggest that toxin producing cyanobacteria could become a threat to users of this over-exploited tropical lake in the near future.

Browsing by Author "Dadheech, Pawan K."

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