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Previous appointments:

KU Medical Center, Kansas City, Kansas, USA.

Research interests:

Studies on the bacterial proteins involved in the transcription and pathogenesis


Address: Department of Biochemistry
Centenary Campus
Bose Institute
P-1/12 C.I.T. Scheme VII-M
Kolkata - 700054, India
E-Mail: sau[at]
Phone: +91-33-25693228


The primary objectives of our research are to study the structure, function, and stability of some bacterial proteins involved in the transcription and pathogenesis. We mostly employ biochemical, biophysical and genetic techniques to characterize our proteins of interest. Currently, we have been working to understand the (1) structure, function, stability of the immunophilins from both Escherichia coli and Staphylococcus aureus, (2) structure, function, stability of an anti-sigma factor from Staphylococcus aureus, (3) structure, function, stability of a global staphylococcal virulence regulator SarA, and (4) architecture of a bacteriophage repressor - operator DNA complex. The yielded data seem to develop tools suitable for gene expression and antibacterial drug discovery.


  1. Polley S, Seal S, Mahapa A, Jana B, Biswas A, Mandal S, Sinha D, Sau K and Sau S (2017) Identification and characterization of a cyclosporin binding cyclophilin from Staphylococcus aureus Newman. Bioinformation. 13:78-85.
  2. Mandal S, Mahapa A, Biswas A, Jana B, Polley S, Sau K, Sau S (2016). A Surfactant-Induced Functional Modulation of a Global Virulence Regulator from Staphylococcus aureus. PLoS One. 11:e0151426.
  3.  Polley S, Chakravarty D, Chakrabarti G, Sau S (2016). Determining the roles of a conserved tyrosine residue in a Mip-like peptidyl-prolyl cis-trans isomerase. Int J Biol Macromol. 87:273-80.
  4.  Polley S, Chakravartya D, Chakrabarti G, Chattopadhyaya R, Sau S (2015) Proline substitutions in a Mip-like peptidyl-prolyl cis-trans isomerase severely affect its structure, stability, shape and activity. Biochimie Open. 1: 28–39.
  5.  Mahapa A, Mandal S, Biswas A, Jana B, Polley S, Sau S, Sau K. (2015) Chemical and thermal unfolding of a global staphylococcal virulence regulator with a flexible C-terminal end. PLoS One. 10: e0122168. IF: 3.234
  6.  Polley S, Jana B, Chakrabarti G, Sau S. (2014) Inhibitor-induced conformational stabilization and structural alteration of a mip-like peptidyl prolyl cis-trans isomerase and its C-terminal domain. PLoS One. 9: e102891. IF: 3.234
  7.  Biswas A, Mandal S, Sau S. (2014) The N-terminal domain of the repressor of Staphylococcus aureus phage Φ11 possesses an unusual dimerization ability and DNA binding affinity. PLoS One. 9: e95012. IF: 3.234
  8.  Jana B and Sau S (2012) The helix  located between the two domains of a Mip-like peptidyl prolyl cis-trans isomerase is crucial for its structure, stability and the protein folding ability. Biochemistry. 51:7930-9. IF: 3.377
  9. Bandhu A, Ganguly T, Jana B, Chakravarty A, Biswas A, and Sau S (2012) Biochemical characterization of L1 repressor mutants with altered operator DNA binding activity. Bacteriophage. 2:79-88.
  10. Jana B, Bandhu A, Mondal R, Biswas A, Sau K, Sau S (2012) Domain Structure and Denaturation of a Dimeric Mip-like Peptidyl-Prolyl cis-trans Isomerase from Escherichia coli. Biochemistry. 51:1223-37.
  11. Luong TT, Sau K, Roux C, Sau S, Dunman PM, and Lee CY (2011) S. aureus ClpC divergently regulates capsule via sae and codY in strain Newman but activates capsule via codY in strain UAMS-1 and in saeS-repaired strain Newman. J Bacteriol. 193: 686-94. 
  12. Bandhu A, Ganguly T, Jana B, Mondal R and Sau S (2010) Regions and residues of an asymmetric operator DNA interacting with the monomeric repressor of temperate mycobacteriophage L1. Biochemistry. 49: 4235-43.
  13. Mondal R, Chanda PK, Bandhu A, Jana B, Lee CY, and Sau S (2010). Detection of the cell wall-affecting antibiotics at sublethal concentrations using a reporter Staphylococccus aureus harboring drp35 promoter – lacZ transcriptional fusion. BMB Rep. 43: 468-473.
  14. Chanda PK, Bandhu A, Jana B, Mondal R, Ganguly T, Sau K, Lee CY, Chakrabarti G,  and Sau S (2010) Characterization of an unusual cold shock protein from Staphylococcus aureus. J Basic Microbiol. 50: 1-8.
  15. Mondal R, Ganguly T, Chanda PK, Bandhu A, Jana B, Sau K, Lee CY, and Sau S (2010). Stabilization of the primary sigma factor of Staphylococcus aureus  by core RNA polymerase. BMB Rep 43: 176-181. 
  16. Ganguly T, Das M, Bandhu A, Chanda PK, Jana B, Mondal R, and Sau S (2009) Physicochemical properties and distinct DNA binding capacity of the repressor of temperate Staphylococcus aureus phage phi11. FEBS J. 276: 1975-85. 
  17. Majumdar T, Chattopadhyay P, Saha DR, Sau S and Mazumder S (2009). Virulence plasmid of Aeromonas hydrophila induces macrophage apoptosis and helps in developing systemic infection in mice. Microb Pathog. 46: 98-107. 
  18. Das M, Ganguly T, Bandhu A, Mondal R, Chanda PK, Jana B and Sau S (2009). Moderately thermostable Cro repressor of the temperate S. aureus phage ф11 possessed novel DNA-binding capacity and physicochemical properties. BMB Rep 42: 160-65. 
  19. Bandhu A, Ganguly T, Chanda K P, Das M, and Sau S (2009) Antagonistic effects of Na+ and Mg2+ on the structure, function and stability of repressor of temperate mycobacteriophage L1. BMB Rep 42: 293-298. 
  20. Chanda PK, Mondal R, Sau K, and Sau S (2009) Antibiotics, arsenate and H2O2 induce the promoter of Staphylococcus aureus cspC gene more strongly than cold. J Basic Microbiol. 49:205-11.
  21. Mandal P, Datta HJ, Sau S and Mandal NC (2008) The delayed early gene G23 of temperate mycobacteriophage L1 regulates the expression of deoxyribonuclease, the product of another delayed early gene of the phage. Pol J Microbiol. 57:113-119.
  22. Sau S, Chattoraj P, Ganguly T, Chanda PK, and Mandal NC (2008) Inactivation of bacterial indispensable proteins by early /delayed early proteins of bacteriophages: Implication in antibacterial drug discovery. Curr Protein Pept Sci 9: 284-90. 
  23. Chattoraj P, Ganguly T, Nandy RK, and Sau S (2008). Overexpression of a delayed early gene hlg1 of temperate mycobacteriophage L1 is lethal to both M. smegmatis and E. coli. BMB Rep. 41: 363-8.
  24. Chanda PK, Ganguly T, Das M, Lee CY, Luong TT and Sau S (2007) Detection of antistaphylococcal and toxic chemicals by biological assay systems developed with a reporter Staphylococcus aureus strain harboring a heat shock promoter – lacZ fusion. J Biochem Mol Biol.  40:936-43. 
  25. Datta HJ, Mandal P, Bhattacharya R, Das N, Sau S, and N. C. Mandal. (2007) The G23 and G25 genes of temperate mycobacteriophage L1 are essential for the transcription of its late genes. J Biochem Mol Biol.  40:156-62. 
  26. Das M, Ganguly T, Chattoraj P, Chanda PK, Bandhu A, Lee CY and Sau S (2007) Overexpression, purification and characterization of repressor of temperate S. aureus phage ф11. J Biochem Mol Biol  40: 740-8. 
  27. Sau K, Gupta SK, Sau S, Mandal SC and Ghosh TC. (2007). Factors influencing the synonymous codon and amino acid usage bias in a broad-host-range Vibrio phage KVP40. J Microbiol. 45: 58-63. 
  28. Ganguly T, Bandhu A, Chanda PK, Chattoraj P, Das M, Mandal NC and Sau S (2007). Purification and characterization of repressor of temperate mycobacteriophage L1. Virol J. 4:64.  
  29. Ganguly T, Chanda PK, Bandhu A, Chattoraj P, Das M and Sau S (2006). Effects of physical, ionic, and structural factors on the binding of repressor of mycobacteriophage L1 to its cognate operator DNA. Protein Pept Lett 13: 793-798. 
  30. K. Sau, S. Sau, S. C. Mandal and T. C. Ghosh. (2006). Factors influencing synonymous codon and amino acid usage biases in Mimivirus. Biosystems 85: 107-13. 
  31. P. Mandal, P. Chakraborty, S. Sau, and N. C. Mandal (2006). Purification and Characterization of a Deoxyriboendonuclease from Mycobacterium smegmatis. J Biochem Mol Biol  39: 140-4. 
  32. K. Sau, S. Sau, S. C. Mandal and T. C. Ghosh. (2005). Factors influencing the synonymous codon and amino acid usage bias in an AT-rich P. aeruginosa phage PhiKZ. Acta Biochim Biophys Sin (Shanghai) 37: 625-33. 
  33. K. Sau, S. K. Gupta, S. Sau, and T. C. Ghosh. (2005). Synonymous codon usage bias in sixteen Staphylococcus aureus phages: Implication in phage therapy. Virus Res 113: 123-31. 
  34. K. Sau, S. K. Gupta, S. Sau, and T. C. Ghosh. (2005). Comparative analysis of the base composition and codon usages in fourteen mycobacteriophage genomes. J Biomol Struct Dyn. 23: 63-72. 
  35. S.K. Gupta, T. Banerjee, S. Basak, K. Sahu, S. Sau, and T.C. Ghosh (2005).  Studies on codon usage in Thermoplasma acidophilum and its possible implications on the occurrences of lateral gene transfer. J Basic Microbiol. 45: 344-354. 
  36. I. Datta, S. Sau, A. Sil and N. C. Mandal. (2005). The Bacteriophage l DNA Replication Protein P Inhibits the oriC DNA- and ATP-binding Functions of the DNA Replication Initiator Protein DnaA of Escherichia coli. J Biochem Mol Biol  38: 97-103.
  37. I. Datta, S. Banik-Maiti, L. Adhikari, S. Sau, N. Das, and N. C. Mandal (2005). The Mutation that makes Escherichia coli Resistant to l P Gene Mediated Host Lethality is Located within the DNA Initiator Gene dnaA of the Bacterium. J Biochem Mol Biol  38: 89-96. 
  38. N. C. Mandal, R. Bhattacharyya, S. Sau, and B. Chaudhuri (2004) Studies on Temperate Mycobacteriophage L1: Its Physical Map, Site of Deletion in one of its Mutant, and Organization of Early, Delayed Early and Late Genes. Perspective in Cytology & Genetics 11: 81-100. Ed. G. K. Manna & S. C. Roy; AICCG Publications, Kolkata.
  39. T. Ganguly, P. Chattoraj, M. Das, P. Chanda, N.C. Mandal, C. Y. Lee, and S. Sau (2004). A point mutation at the C-terminal half of the repressor of temperate Mycobacteriophage L1 affects its binding to the operator DNA. J Biochem Mol Biol  37: 709-714. 
  40. K. Sahu, S. K. Gupta, S. Sau, and T. C. Ghosh (2004). Synonymous Codon Usage Analysis of Mycobacteriophage Bxz1 and its plating bacteria M. smegmatis: identification of the Highly and Lowly Expressed Genes of Bxz1 and the possible function of its tRNA species. J Biochem Mol Biol  37: 487-92. 
  41. S. Sau, P. Chattoraj, T. Ganguly, C. Y. Lee, and N. C. Mandal (2004). Cloning and Sequencing Analysis of the Repressor Gene of Temperate Mycobacteriophage L1. J Biochem Mol Biol  37: 254 -259. 
  42. C. Chattopadhyay, S. Sau, and N. C. Mandal. (2003). Cloning and Characterization of the Promoters of Temperate Mycobacteriophage L1. J Biochem Mol Biol  36: 586 - 592.
  43. L. Thanh, S. Sau, Gomez M, J. C. Lee and C. Y. Lee (2002). Regulation of Staphylococcus aureus Capsular Polysaccharide Expression by agr and sarA. Infect Immun 70: 440 -50. 
  44. J.L. Snodgrass, N. Mohammad, J.M. Ross, S. Sau, Chia. Y. Lee and M.S. Smeltzer (1999). Functional analysis of the S.aureus collagen adhesin B domain. Infect Immun. 67:3952-9.
  45. Ouyang Shu, S. Sau and Chia Y. Lee (1999). Promoter analysis of the cap8 operon involved in type 8 capsular polysaccharide production in Staphylococcus aureus. JBacteriol, 181: 2492 –2500. 
  46. P. Gilpsey, Chia Y. Lee , S. Sau and M.S. Smeltzer (1998). Factors Affecting the Collagen Binding Capacity of Staphylococcus aureus. Infect Immun, 66: 3170-3178. 
  47. S. Sau., Navneet Bhasin, Elisabeth R.Wann, J. C. Lee, T. J. Foster and  C. Y. Lee (1997). The Staphylococcus aureus  Allelic Genetic Loci for  Serotype 5 and 8 Capsule Expression Contain the Type-specific Genes Flanked by Common Genes. Microbiology143: 2395-2405.
  48. S. Sau, Jiwen Sun and Chia Y. Lee (1997). Molecular Characterization and Transcriptional Analysis of Type 8 Capsule Genes in S. aureus. JBacteriol, 179: 1614-1621.
  49. S. Sau and Chia Y. Lee (1996). Cloning of Type 8 Capsule Genes and Analyses of Gene Clusters for the Production of Different Capsular Polysaccharides in Staphylococcus aureus. JBacteriol, 178: 2118-2126.
  50. B. Chaudhuri, S. Sau, H. J. Datta and N.C. Mandal (1993). Isolation, Characterization and Mapping of Temperature Sensitive Mutations in the Genes Essential for Lysogenic and Lytic growth of the   Mycobacteriophage L1. Virology, 194: 166-172.
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    The following courses were taught:

    1. Molecular Microbiology

    2. Radiochemical Methods

    3. Radiological Safety


    Image Name Designation Department Campus Contact number Email
    profile image Soham Seal SRF Biochemistry Centenary 25693238 sealsoham16
    profile image Soumitra Polley SRF Biochemistry Centenary 25693228 s_polley
    profile image Sukhendu Mandal SRF Biochemistry Centenary 25693238


    1. Mr. Anindya Biswas:
    2. Mr. Sukhendu Mondal:
    3. Mr. Soumitra Polley: 
    4. Mr. Debabrata Sinha:
    5. Mr. Soham Seal:

    Group News:

    Our recent research outputs:

    Ø  SarA, a global virulence regulator in Staphylococcus aureus, is a single domain protein with a long, flexible C-terminal end.

    Ø  The chemical-induced equilibrium unfolding of SarA occurs via the formation of at least two stable intermediates.

    Ø  Triton X-100 has significantly enhanced the DNA binding activity of SarA most possibly by altering its structure.

    Ø  A repressor of staphylococcal phage Փ11 and its N-terminal domain exist as the dimers in the solution, bind to the operators with similar affinity, affect the binding of RNA polymerase to the putative Փ11 promoters, and bind to the operator DNA as a dimer.

    Ø  The operator binding mechanism of Φ11 repressors differs significantly from those of other phage repressors.

    Ø  FKBP22, a peptidyl-prolyl cis-trans isomerase encoded by Escherichia coli, carries two domains, which are separated by a long α-helix. While N-terminal domain is involved in dimerization, the C-terminal domain of FKBP22 binds inhibitors such as rapamycin and FK506.

    Ø  Binding of inhibitors to FKBP22 and its C-terminal domain have enhanced their thermodynamic stability.

    Ø  The domain-connecting helix in FKBP22 is indispensable for preserving its structure, function, stability and shape.

    Ø  A conserved tyrosine residue in the N-terminal domain of FKBP22 is critical for its dimerization ability, structure, and function.

    Ø  Staphylococcus aureus encodes a cyclophillin-type of peptidyl-prolyl cis-trans isomerase as it specifically shows binding to cyclosporin A.

    Ø  Binding of cyclosporin A to cyclophilin has enhanced its thermodynamic stability.

    Ø  The chemical-induced unfolding of cyclophilin or inhibitor bound-cyclophilin occurs by a three-state mechanism.