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Abstract The wet soil-inhabiting cyanobacterium URH-6-PS was collected from the state of Tripura, India, and characterized using a polyphasic approach. Initial microscopic analysis indicated the strain to be a member of the genus Cylindrospermum, however, the 16S rRNA gene phylogenetic analysis showed some interesting results. The strain URH-6-PS clustered in the Clade I, which positioned itself outside the Cylindrospermum sensu stricto clade with strong probability/bootstrap support, indicating that the strain may not belong to the genus Cylindrospermum. Further, analysis of the 16S–23S ITS region using the folded secondary structures of the D1-D1′, Box-B, and V3 helices and the 16S–23S ITS percentage dissimilarity values clearly indicated the distinctiveness of strain URH-6-PS from other members of the Clade I. The detailed investigations conducted in this study provided sufficient evidence that the taxonomic status of the members of Clade I need to be revised. Interestingly, all members of the clade I originated from tropical and subtropical habitats while members of the Cylindrospermum sensu stricto clade have been reported from temperate conditions. Previous studies had also indicated the possibility of the formation of tropical and subtropical Cylindrospermum-like genera, and thus this comes across as a much-awaited study to resolve the taxonomic complexities around the genus Cylindrospermum. Based on the results obtained in this study and the trends observed in the earlier studies, we describe a novel Cylindrospermum-like genus Johanseniella gen. nov., with the type species Johanseniellatripurensis sp. nov. in accordance with the International Code of Nomenclature for algae, fungi, and plants. A new cyanobacterial genus was isolated from Tripura, Northeast India.

The Aedes ( Stegomyia ) albopictus (Skuse, 1895) (Diptera: Culicidae) is one of the major vectors for Dengue and Chikungunya. However, our study uncovered another mosquito species morphologically similar to Ae. albopictus but is genetically different. The male genitalia of this species possess minute differences in the IX tergum with Ae. albopictus . Nucleotide diversity and mean genetic distance analysis confirmed the genetic difference from Ae. albopictus and other Aedes species. However, this species has a significant degree of genetic similarity with the cryptic species of Ae. albopictus earlier reported from Vietnam and China. The time tree revealed the median divergence time of this species and Ae. albopictus species to be approximately 36.13 million years ago. This study marks the discovery of an Aedes nr. Albopictus species resembling Ae. albopictus in India and third in the world, also reports the distinct morphological feature of the male genitalia for the first time. Our study indicates the sympatric behavior of this species as it shares the breeding habitat of Ae. albopictus . The absence of endosymbiont Wolbachia in this species raises the possibility of reproductive isolation with Ae. albopictus leading to sympatric speciation and increasing virus-carrying capability for this species, having significant implications for vector-borne disease control.

Landslides are one of the most extensive and destructive geological hazards on the globe. Tripura, a northeastern hilly state of India experiences landslides almost every year during monsoon season causing casualties and huge economic losses. Hence, it is required to assess the landslide susceptibility of the area that would support short- and long-term planning and mitigation. The analytic hierarchy process (AHP) integrated with geospatial technology has been adopted for landslide susceptibility mapping in the state. Eight influencing factors such as slope, lithology, drainage density, rainfall, land use land cover, distance from rivers and roads, and soil type were selected to map the landslide susceptibility. Landslide susceptibility index (LSI) was found to vary from 6.205 during monsoon to 1.427 during post-monsoon season. The LSI values were classified into very high, high, moderate, low, and very low susceptibility. Landslide susceptibility maps for three different seasons, namely, pre-monsoon, monsoon, and post-monsoon, were prepared. The study showed that most of the areas of the state come under very low to moderate landslide susceptibility zones. Around 73.2% area of the state is found to be under low landslide-susceptible zones during the pre-monsoon season, around 62% area is prone to landslides with moderate susceptibility during the monsoon season, and 68.5% area comes under landslides with low susceptibility zones during the post-monsoon season. The results of this study may be referred to the engineers and planners for the assessment, control, and mitigation of landslides and the development of basic infrastructure in the state.

In West Tripura district, river bank erosion becomes very common during monsoons along the Haora River and the Sonai Gang. Erosion occurs across 45.39 km (96% of the total length) of the Haora River and 20.12 km (90% of the total length) along the Sonai Gang. The main cause of river bank erosion in the district is the nature of bank material with respect to its erodibility factor (resisting force). The objectives of this study were to identify the nature of bank material of the rivers in West Tripura district and to analyse the shear strength of these materials. Samples were collected from twelve sites at various depths from top of the river bank up to the water level. Hydrometer test and grain size were also analysed. Uniformity coefficient (Cu ) and coefficient of curvature (Cc ) were calculated to identify the shear strength of bank soil. Tests revealed that the bank soils contain more than 90% sand and less percentage of silt and clay. This makes the soil non-cohesive and leads to maximum erosion.

Conventional methods of determination of water quality index are main and popular approach to indicate surface water quality status. The present study tried to endeavor a unique index method which will be beneficial for any water quality parameters irrespective of places and water uses making calculation easy and less complex. In the present study, eight sampling stations and seven physiochemical parameters were selected based on citation frequency. Multi-criteria decision-making technique such as analytical hierarchical process was taken into account to determine weights of each selected parameter along with measuring attractiveness by a categorical based evaluation technique to validate the result. National Sanitation Foundation Water Quality Index was also used to compare results from new methodology with the results from existing conventional technique. Analytical hierarchical process showed SP5 is more affected than other stations which are similar to result from conventional method where both outcomes fall in the same range though values are different. It can be concluded that using multi-criteria decision-making techniques in water quality calculation is significant as it gives definite values with more accuracy and less effort making the process simple and less complex where different types of water use can be considered. Development of water quality index will be more accurate with increasing number of sampling stations, monthly variation of data set, continuous monitoring considering other conventional methods and multi-criteria decision-making techniques.

The northeast region of India is highlighted as the most vulnerable region for malaria. This study attempts to explore the epidemiological profile and quantify the climate-induced influence on malaria cases in the context of tropical states, taking Meghalaya and Tripura as study areas. Monthly malaria cases and meteorological data from 2011 to 2018 and 2013 to 2019 were collected from the states of Meghalaya and Tripura, respectively. The nonlinear associations between individual and synergistic effect of meteorological factors and malaria cases were assessed, and climate-based malaria prediction models were developed using the generalized additive model (GAM) with Gaussian distribution. During the study period, a total of 216,943 and 125,926 cases were recorded in Meghalaya and Tripura, respectively, and majority of the cases occurred due to the infection of Plasmodium falciparum in both the states. The temperature and relative humidity in Meghalaya and temperature, rainfall, relative humidity, and soil moisture in Tripura showed a significant nonlinear effect on malaria; moreover, the synergistic effects of temperature and relative humidity (SI=2.37, RERI=0.58, AP=0.29) and temperature and rainfall (SI=6.09, RERI=2.25, AP=0.61) were found to be the key determinants of malaria transmission in Meghalaya and Tripura, respectively. The developed climate-based malaria prediction models are able to predict the malaria cases accurately in both Meghalaya (RMSE: 0.0889; R 2 : 0.944) and Tripura (RMSE: 0.0451; R 2 : 0.884). The study found that not only the individual climatic factors can significantly increase the risk of malaria transmission but also the synergistic effects of climatic factors can drive the malaria transmission multifold. This reminds the policymakers to pay attention to the control of malaria in situations with high temperature and relative humidity and high temperature and rainfall in Meghalaya and Tripura, respectively.

Forest-dependent indigenous communities rely on natural resources for their livelihoods, but those are currently under threat due to many factors, including the adverse impact of climate change. The present study looks into climate change-related perception and adaptation strategies of three forest-dependent indigenous communities, namely, Khasia, Tripura and Garo in the Lawachara National Park of Northeastern Bangladesh. Household surveys, focus group discussions, key informant interviews, and observation methods were used to unveil the climatic events, impacts and related adaptations. The events include the change in temperature and rainfall patterns, landslide, soil erosion and flash flood, heavy cold and fog, and natural calamities. Moreover, livelihood problems emanating from these events are the drying up of streams and wells, irregular rainfall, increased dieback and mortality of seedlings, pests, diseases, and the attack of crops by wild animals. Likewise, the reduction of soil moisture content, growing season and crop productivity, landslides, damage of roads and culverts, and increased human diseases are common. This study recognized 29 adaptation strategies and divided them into six management categories, drawing on their local knowledge of the natural resources and other technologies. The study reveals that, although adaptation strategies through land use and land cover changes are not enough to sustain their livelihoods, the tactics help them to reduce the risk of, and increase food security and community resilience against, climate change.

Background Malaria continues to be a major public health problem in the Northeastern part of India despite the implementation of vector control measures and changes in drug policies. To develop successful vaccines against malaria, it is important to assess the diversity of vaccine candidate antigens in field isolates. This study was done to assess the diversity of Plasmodium falciparum AMA-1 vaccine candidate antigen in a malaria-endemic region of Tripura in Northeast India and compare it with previously reported global isolates with a view to assess the feasibility of developing a universal vaccine based on this antigen. Methods Patients with fever and malaria-like illness were screened for malaria and P. falciparum positive cases were recruited for the current study. The diversity of PfAMA-1 vaccine candidate antigen was evaluated by nested PCR and RFLP. A selected number of samples were sequenced using the Sanger technique. Results Among 56 P. falciparum positive isolates, Pfama-1 was successfully amplified in 75% (n = 42) isolates. Allele frequencies of PfAMA-1 antigen were 16.6% (n = 7) for 3D7 allele and 33.3% (n = 14) in both K1 and HB3 alleles. DNA sequencing revealed 13 haplotypes in the Pfama-1 gene including three unique haplotypes not reported earlier. No unique amino-acid substitutions were found. Global analysis with 2761 sequences revealed 435 haplotypes with a very complex network composition and few clusters. Nucleotide diversity for Tripura (0.02582 ± 0.00160) showed concordance with South-East Asian isolates while recombination parameter (Rm = 8) was lower than previous reports from India. Population genetic structure showed moderate differentiation. Conclusions Besides documenting all previously reported allelic forms of the vaccine candidate PfAMA-1 antigen of P. falciparum , new haplotypes not reported earlier, were found in Tripura. Neutrality tests indicate that the Pfama-1 population in Tripura is under balancing selection. This is consistent with global patterns. However, the high haplotype diversity observed in the global Pfama-1 network analysis indicates that designing a universal vaccine based on this antigen may be difficult. This information adds to the existing database of genetic diversity of field isolates of P. falciparum and may be helpful in the development of more effective vaccines against the parasite.