10.22376/ijpbs.2019.10.1.p1-12 Volume 1 Issue 2 2010 (April - June) As a part of systematic investigation of synthesis and biological activity of several new 2-(2'-substituted-benzylidene-hydrazino-acetyl)-mercapto-5-methyl-1,3,4-thiadiazoles, lessThan b greaterThan 3(a-n) lessThan /b greaterThan and 2-[2'-{4-substituted-aryl-3-chloro-2-oxo-azetidine}-acetyl-amino-mercapto]-5-methyl-1,3,4-thiadiazoles, lessThan b greaterThan 4(a-n) lessThan /b greaterThan have been synthesized from 2-(2'-hydrazino-acetyl)-mercapto-5-methyl-1,3,4-thiadiazoles, lessThan b greaterThan 2 lessThan /b greaterThan using 5-methyl-1,3,4-thiadiazole-2-thiol as the starting material. All the synthesized products were evaluated for their antibacterial activity against lessThan i greaterThan Bacillus substilis, Escherichia coli. Klebsiella pneumoniae lessThan /i greaterThan and lessThan i greaterThan Streptococcus aureus lessThan /i greaterThan bacteria and antifungal activity against lessThan i greaterThan Aspergillus niger, Aspergillus flavus, Fusarium oxisporium lessThan /i greaterThan and lessThan i greaterThan Trichoderma viride lessThan /i greaterThan fungi respectively. The structures of all the synthesized compounds have been determined by their spectral and microanalytical data. Rajiv Dua,S. K. Srivastava 5-Methyl-1,3,4-thiadiazole-2-thiol, benzylidenes, 2-oxo-azetidines, antimicrobial activity. -