ossil remains from ~100 million years ago (Ma) show that snakes were widely distributed across the world by the late Cretaceous period 1. During the course of their evolution, snakes lost their limbs, acquiring a serpentine body 2. Some also evolved or co-opted venom systems to help subdue, capture and digest their prey 2,3. The Colubroides clade of advanced snakes encompasses >3,000 extant species including >600 venomous species 4. The most venomous snakes include the true vipers and pit vipers, both members of the Viperidae family, and cobras, kraits, mambas and sea snakes from the Elapidae family 5. Although humans are not an intended target, accidental contact with venomous snakes can be deadly. Snakebite envenoming is a serious neglected tropical disease that affects ~5 million people worldwide annually, leading to ~400,000 amputations and >100,000 deaths 6. In India alone, the high rural population density combined with the presence of the 'big four' deadly snakes, namely the Indian cobra (Naja naja), Russell's viper (Daboia russelli), sawscaled viper (Echis carinatus) and common krait (Bungarus caeruleus), results in >46,000 snakebite-related deaths annually 7. Snake venom is a potent lethal cocktail rich in proteins and peptides, secreted by specialized venom gland cells. Venom components can be broadly classified as neurotoxic, cytotoxic, cardiotoxic or hemotoxic, and the composition can vary both between and within species 8-11. Currently, snake antivenom is the only treatment effective in the prevention or reversal of the effects of envenomation. Since 1896, antivenom has been developed by immunization of large mammals, such as the horse, with snake venom to generate a cocktail of antibodies that are used for therapy 12. Given the heterologous nature of these antibodies, they often elicit adverse immunological responses when treating snakebite victims 13. Moreover, the antivenom composition is not well defined and its ability to neutralize the venom

BackgroundThe oral cavities of snakes are replete with various types of bacterial flora. Culture-dependent studies suggest that some of the bacterial species are responsible for secondary bacterial infection associated with snakebite. A complete profile of the ophidian oral bacterial community has been unreported until now. Therefore, in the present study, we determined the complete bacterial compositions in the oral cavity of some snakes from India.MethodsTotal DNA was isolated from oral swabs collected from three wild snake species (Indian Cobra, King Cobra and Indian Python). Next, the DNA was subjected to PCR amplification of microbial 16S rRNA gene using V3-region-specific primers. The amplicons were used for preparation of DNA libraries that were sequenced on an Illumina MiSeq platform.ResultsThe cluster-based taxonomy analysis revealed that Proteobacteria and Actinobacteria were the most predominant phyla present in the oral cavities of snakes. This result indicates that snakes show more similarities to birds than mammals as to their oral bacterial communities. Furthermore, our study reports all the unique and common bacterial species (total: 147) found among the oral microbes of snakes studied, while the majority of commonly abundant species were pathogens or opportunistic pathogens to humans. A wide difference in ophidian oral bacterial flora suggests variation by individual, species and geographical region.ConclusionThe present study would provide a foundation for further research on snakes to recognize the potential drugs/antibiotics for the different infectious diseases.Electronic supplementary materialThe online version of this article (10.1186/s40409-018-0181-8) contains supplementary material, which is available to authorized users.

The tiger, a poster child for conservation, remains an endangered apex predator. Continued survival and recovery will require a comprehensive understanding of genetic diversity and the use of such information for population management. A high-quality tiger genome assembly will be an important tool for conservation genetics, especially for the Indian tiger, the most abundant subspecies in the wild. Here, we present high-quality near-chromosomal genome assemblies of a female and a male wild Indian tiger (Panthera tigris tigris). Our assemblies had a scaffold N50 of >140 Mb, with 19  scaffolds corresponding to the 19 numbered chromosomes, containing 95% of the genome. Our assemblies also enabled detection of longer stretches of runs of homozygosity compared to previous assemblies, which will help improve estimates of genomic inbreeding. Comprehensive genome annotation identified 26,068 protein-coding genes, including several gene families involved in key morphological features such as the teeth, claws, vision, olfaction, taste, and body stripes. We also identified 301 microRNAs, 365 small nucleolar RNAs, 632 transfer RNAs, and other noncoding RNA elements, several of which are predicted to regulate key biological pathways that likely contribute to the tiger's apex predatory traits. We identify signatures of positive selection in the tiger genome that are consistent with the Panthera lineage. Our high-quality genome will enable use of noninvasive samples for comprehensive assessment of genetic diversity, thus supporting effective conservation and management of wild tiger populations.

The tiger, a poster child for conservation, remains an endangered apex predator. Continued survival and recovery will require a comprehensive understanding of their genetic diversity and the use of such information for population management. A high-quality tiger genome assembly will be an important tool for conservation genetics, especially for the Indian tiger, the most abundant subspecies in the wild. Here, we present high-quality near-chromosomal genome assemblies of a female and a male wild Indian tiger (Panthera tigris tigris). Our assemblies had a scaffold N50 of >140 Mb, with 19 scaffolds, corresponding to the 19 numbered chromosomes, containing 95% of the genome. Our assemblies also enabled detection of longer stretches of runs of homozygosity compared to previous genome assemblies which will improve estimates of genomic inbreeding. Comprehensive genome annotation identified 26,068 protein-coding genes, including several gene families involved in key morphological features such as the teeth, claws, vision, olfaction, taste and body stripes. We also identified 301 microRNAs, 365 small nucleolar RNAs, 632 tRNAs and other noncoding RNA elements, several of which are predicted to regulate key biological pathways that likely contribute to tiger’s apex predatory traits. We identify signatures of positive selection in the tiger genome that are consistent with the Panthera lineage. Our high-quality genome will enable use of non-invasive samples for comprehensive assessment of genetic diversity, thus supporting effective conservation and management of wild tiger populations.

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