Dr Varsha Singh

Research interests

Olfaction, odours and microbiomes

Odours are produced by most microbes and many plants. They are small molecules (300 Da or less) bearing alcohol, aldehyde, ester, aldehyde groups or containing cyclic moieties. They originate from common primary metabolites using unique enzymes encoded in microbial genomes. They serve as signals for intra species, inter species and interkingdom signals. They can also be antimicrobial, antiparasitic agents and pathogen associated molecular patterns [Prakash et al., EMBO J 2021].

Olfaction is the most ancient sensory modality but relatively poorly understood. Elephants have 2000 Odorant receptors (ORs), humans have 400 and a worm has close to 400. They make up 3% of all the genes in the human genome. Odorant receptors (ORs) are present not only in human nose but also in the intestine, lungs, kidney, pancreas, liver, sperm and other tissues where they might help in sensing the resident community of microbes called the ‘microbiome’.

Microbiome is a community of bacteria, fungi and viruses in the gut, lungs, skin, reproductive tract of animals. In the Singh laboratory, we focus on the microbiome of mouse gut and human vagina by isolating culturable microbial taxa and identifying odours they produce. We are specifically interested in identifying microbes contributing to unexplained infertility.

Fundamental research 

• How are odours made in bacterial cells? 
• Does odour landscape of microbiome changes in ageing mice?
• Mechanistic bases of GPCR-odour interactions
• Deorphanizing olfactory GPCRs

Translational and interdisciplinary research 

Biomarker Discovery Project: 

Odours as biomarkers of infection, neurodegenerative diseases and unexplained infertility (interdisciplinary work involving clinicians at Ninewells hospital)

E-nose for infectious disease: 

Electronic nose for sensing biomarkers of pulmonary infection in exhaled breath (interdisciplinary collaboration with Leverhulme Centre for Forensic Science LRCFS)

Approaches

Odour identification: using gas-chromatography mass spectrometry (GC-MS/MS) in combination with microbial genetics. 

GPCR studies: 

1. Gene editing using CRISPR/CAS9 to create repertoire of odorant receptor mutants in Caenorhabditis elegans, a round worm
2. to identify and study ORs involved in regulation of metabolism and longevity, 
3. to study function of ORs of human sperm 

What else?

We utilize Pseudomonas aeruginosa, a Gram-negative bacterium, to understand how it utilizes its large genomic repertoire of histidine kinase sensors to identify and compete with other microbes, in the context of respiratory infections including pneumonia. 

Who we are

The Singh laboratory has 4 PhD students, 2 master’s students and a PDRA (incoming) apart from Varsha. We welcome others interested in olfaction, odours and microbiome to join us. Apart from really pleasant odours (some offensive ones), we do have a lovely view of the river Tay from our lab.

Our collaborators

• Dr Isabel Beets, KU Leuven, Belgium
  • new tools for GPCR deorphanization
• Dr Charis Marwick, School of Medicine, University of Dundee 
  • Biomarkers Discovery project on E. coli bacteraemia
  • funded by Tenovus Scotland
• Dr Sarah Martins Da Silva School of Medicine, University of Dundee
  • Biomarkers Discovery project for women’s health and unexplained infertility
  • funded by Tenovus Scotland
• Dr James Abbott, University of Dundee
  • Metagenomics for vaginal microbiome and mice gut microbiota projects
• Prof. Jens Janushke, University of Dundee
  • Convergent evolution of microbiomes of animals
• Dr Oluwasesan Adegoke, LRCFS, UoD
  • Diagnostic  sensors for microbial odours
  • funded by Cunningham Trust

Funding support

• Wolfson Fellowship from the Royal Society
• Tenovus Scotland (grant and PhD studentship)
• Cunningham Trust (PhD studentship)

Openings

Postdoctoral Fellow 

We welcome applicants for postdoc positions in our research group. If you are interested in any of the following areas, write to Varsha at [email protected]

• Olfaction, odorant GPCRs and microbiomes
• Genetic basis of anosmia in Parkinson’s Disease
• Electronic nose for odour biomarkers of disease

If you are interested in working at the cross section of microbiology, immunology and neuroscience, do get in touch.  

PhD Openings will be advertised on this webpage.

M Res Openings can be found on the Life Sciences Master of Research MSc (Res) course page.

Select publications

See Google scholar page for a full list of publications at https://scholar.google.com/citations?hl=en&user=TNeCGC8AAAAJ&view_op=list_works

Siddiqui R., Mehta N., Ranjith G., Felix M.A., Chen C.,  Singh, V. Olfactory basis for essential amino acid perception during foraging in Caenorhabditis elegans.eLife 2026 Apr 24 DOI: 10.7554/eLife.101936.3

Pradhan D, Tanwar A, Wong J, Parthasarathi S, Frankel GM, Singh V. Toroidal displacement of Klebsiella pneumoniae by Pseudomonas aeruginosa is a unique mechanism to avoid competition for iron. mBio. 2025 Jul 9;16(7):e0114925. DOI: 10.1128/mbio.01149-25

Badal D, Kumar A, Singh V, Raj M D. Dynamic fluid layer around immotile yeast colonies mediates the spread of bacteria. Biophys J. 2025 Jun 17;124(12):1918-1929. DOI: 10.1016/j.bpj.2025.04.022

Venkatesh, S., Siddiqui R., Sandhu, A., Ramani, M., Houston I.R., Watts J.L., Singh, V. Homeostatic control of stearoyl desaturase expression via patched-like receptor PTR-23 ensures the survival of C. elegans during heat stress. PLoS Genet. 2023 18;19(12):e1011067 DOI: 10.1371/journal.pgen.1011067 

Ambreetha, S., Singh, V. Genetic and environmental determinants of surface adaptations in Pseudomonas aeruginosa.     Microbiology 2023 169 (6), 001335 DOI: 10.1099/mic.0.001335 

Venkatesh, S., Singh, V. Amphid Sensory neurons of Caenorhabditis elegans orchestrate its survival from broad classes of pathogens. Life Science Alliance 2023 6 (8)  DOI: 10.26508/lsa.202301949 

Pradhan, D., Tanwar, A., Parthsarathy, S. and Singh, V. Toroidal displacement of Klebsiella pneumoniae by Pseudomonas aeruginosa is a unique mechanism to avoid competition for iron. bioRxiv (preprint) https://doi.org/10.1101/2022.09.21.508880

Filipowicz, A., Aballay, A., Singh, V. Cellular and Organismal Responses to Infections in Caenorhabditis elegans. Elsevier DOI:10.1016/B978-0-12-821618-7.00043-2. 

Prakash, D., Siddiqui R., Chalasani S., Singh, V. Pyrrole produced by Pseudomonas aeruginosa influences olfactory food choice of Caenorhabditis elegans.  bioRxiv (Preprint)      https://doi.org/10.1101/2022.01.27.477966

Badal, D., Jayarani, A.V., Kollaran, M.A., Prakash, D., Monisha P., Singh, V. Foraging signals promote swarming in starving Pseudomonas aeruginosa. mBio 2021, 12(5):02033-21. https://doi.org/10.1128/mBio.02033-21 

Prakash, D., Akhil, M.S., Radhika, B., Venkatesan, R., Chalasani, S.H., Singh, V. 1-Undecene from Pseudomonas aeruginosa is an olfactory signal for flight or fight response in Caenorhabditis elegans. EMBO J. 2021, e106938. https://doi.org/10.15252/embj.2020106938 (OPEN ACCESS)

Sandhu, A., Badal, D., Sheokand, R., Tyagi, S., Singh V. Specific collagens maintain the cuticle permeability barrier in Caenorhabditis elegans. GENETICS 2021, 217(3):iyaa047. https://doi.org/10.1093/genetics/iyaa047 (OPEN ACCESS)

Venkatesh, S.R., Singh, V. G protein-coupled receptors: The choreographers of innate immunity in Caenorhabditis elegans. PLoS Pathog 2021, 17(1): e1009151. https://doi.org/10.1371/journal.ppat.1009151 (OPEN ACCESS)

Dixit, A., Singh, V. The brain-gut axis of longevity. Aging (Albany NY) 2020,12(18):17754-17755. doi: 10.18632/aging.103996. Epub ahead of print. PMID: 32986014; PMCID: PMC7585115. 

Prakash, P., Abdulla A.Z., Singh, V., Varma, M.M. Swimming statistics of cargo-loaded single bacteria. Soft Matter 2020, 100: 062609. 

Dasgupta, M., Shashikanth, M.,  Gupta, A.,  Sandhu, A., De, A., Javed, S.,  Singh, V.  NHR-49 transcription factor regulates immuno-metabolic response and 1 survival of Caenorhabditis elegans during Enterococcus faecalis infection. Infec Immun. 2020, 88(8):e00130-20 (full text) https://doi.org/10.1128/IAI.00130-20 (OPEN ACCESS)

Dixit, A., Sandhu, A., Modi, S., Shashikanth, M., Koushika, S., Watts, J., Singh, V. Neuronal control of lipid metabolism by STR-2 G protein-coupled receptor promotes longevity in C. elegans. AGING CELL 2020, 19(6):e13160 (full text) https://doi.org/10.1111/acel.13160  (OPEN ACCESS)

Kollaran, M.A., Joge, S., Harshitha, K., Badal,  D., Prakash, D., Mishra, A., Varma, M.M. and Singh, V. Context-Specific Requirement of Forty-Four Two-Component Loci in Pseudomonas aeruginosa Swarming. iScience. 2019 Mar 29;13: 305-317. https://doi.org/10.1016/j.isci.2019.02.028

Gupta, A., Singh, V., (2017). GPCR Signaling in C. elegans and Its Implications in Immune Response. In Advances in immunology (Vol. 136, pp. 203-226). Academic Press. [Book Chapter], doi: 10.1016/bs.ai.2017.05.002

Sun, J., Singh, V., Kajino-Sakamoto, R., Aballay, A. Neuronal GPCR controls innate immunity by regulating non-canonical unfolded protein response genes. Science 2011, 332(6030):729-32. doi: 10.1126/science.1203411.

Styer, K.L., Singh, V., Macosko, E., Steele, S.E., Bargmann, C.I., Aballay, A. Innate immunity in Caenorhabditis elegans is regulated by neurons expressing NPR-1/GPCR. Science 2008, 322(5900), pp.460-464. doi:10.1126/science.1163673

Singh, V., Aballay, A. Heat-shock transcription factor (HSF)-1 pathway required for Caenorhabditis elegans immunity. Proceedings of the National Academy of Sciences 2006, 103(35), pp.13092-13097. doi:10.1073/pnas.0604050103 

• BS32036 Molecular Microbiology (Module Manager)
• BS42009 Advanced Molecular Microbiology
• BS31026 Cell Biology