Therapeutic properties of Haladaptatus sp. strain R4 Urmimala Sen, Subhra Kanti Mukhopadhyay Department of Microbiology, The University of Burdwan, Burdwan, West Bengal, India. Mail ID of Urmimala Sen: email@example.com Mail ID of Subhrakanti Mukhopadhyay: firstname.lastname@example.org Haladaptatus sp strain R4 has been isolated from SreeMa saltern of Ramnagar, West Bengal, India. Salterns of this area are having wide prokaryotic diversity that can be utilized in the field of bioprospecting in pharmaceutical industry, agriculture and environmental cleaning. Strain R4 being a member of genus Haladaptatus is euryhaline in nature, capable of withstanding wide salinity range and complete absence of NaCl for many hours. Haladaptatus sp strain R4 is loaded with enzymes and proteins of therapeutic values. The strain codes for anti-cancer enzymes like L-Asparaginase and L-Glutaminase. Both the enzymes are reported to be used as chemotherapeutic agents to treat variety of lymphoproliferative disorders and lymphomas particularly Acute Lymphoblastic Leukaemia (ALL) and Hodgkin’s lymphoma. N-acyl homoserine lactone dependent quorum sensing is related to virulence in Gram-negative pathogens. Strain R4 produces two quorum quenching enzymes N-Acyl-Homoserine Lactone Lactonase and acylase that can destroy the structure of N-acyl homoserine lactone. Thus pathogenicity would be destroyed without insertion of any drug inside the pathogen, avoiding resistance complications (antibiotic resistance is an emerging problem in today’s antibiotic dependant pathogen therapy). This archaea is special in having both “salt-in-cytoplasm” and “organic osmolyte” mechanism to withstand the osmotic shock of its environment. Glycine betaine along with trehalose is compatible solutes of strain R4. Glycine betaine can stabilize cells under salt, temperature or desiccation stress. The archaea can be used as a novel “cell factory” of glycine betaine for “Bacterial Milking”. “Bacterial Milking” is a biotechnological process where prokaryotic cells can be used for production of compatible solutes by giving osmotic stress. The strain is having a retinal like pigment with strong UV-absorbing and anti-oxidant properties. Retinal is another name of miracle in skin care. It reduces sun damage, wrinkles and known for cell renewal. Production of Poly-Hydroxy Butyrate (PHB) by this strain adds to its applicability in environmental cleaning. Production of enzymes like cellulase, amylase, lipase, protease, tryptophanase and phosphate solubilisation are also observed in vitro and in silico. ANI value of Haladaptatus sp strain R4 with its closest relative Haladaptatus paucihalophilus DX253 calculated in Kostas Lab, IMG JGI and EzBioCloud is less than 95%, revealing the fact that strain R4 is a new species within the genus Haladaptatus. Strain R4 is a pink colored coccus which grows optimally at 37oC, 3M NaCl, pH 5.5 and 2% Mg++ ion concentration. It is a catalase, indole and MR (Methyl Red Test) positive and VP (Vogues-Proskauer Test) negative strain. It is positive for nitrate reduction test. The strain is capable of utilizing a number of carbohydrates starting from Dextrose, Lactose, Galactose, Maltose, Fructose, Sucrose, L-arabinose, Mannose, Sorbitol, Mannitol and many more. Strain R4 grows in presence of heavy metals like arsenic, lead, cadmium, chromium and mercury. The strain is sensitive to all the antibiotics tested. The tested antibiotics are Bacitracin, Chloramphenicol, Gentamycin, Vancomycin, Penicillin-G, Neomycin, Polymyxin-B, Rifampicin and Nalidixic acid. Pathogenicity Island, antibiotic resistance genes and coagulase gene are not coded in the whole genome of the strain. Hence, it can be concluded that this archaea is not harmful to the eukaryotes. Haladaptatus sp strain R4 could be used as a potential novel archaeal source of therapeutic agents. The whole-genome has been deposited at DDBJ/ENA/GenBank under the accession number LWHG00000000. RefSeq Identifier is GCF_001625445.1. The 16S rDNA sequence is deposited at NCBI with accession number KT174478.