Isolation and characterisation of a novel Podoviridae-phage infecting Weissella cibaria N 22 from Nham, a Thai fermented pork sausage

Abstract

A novel . Podoviridae lactic acid bacteria (LAB) phage from Nham, a Thai fermented pork sausage, is reported. From a total of 36 samples, 41 isolates of LAB were obtained and employed as hosts for the isolation of phages. From these LAB, only one phage, designated . Φ 22, was isolated. The lactic acid bacterial isolate named N 22, sensitive to phage . Φ 22 infection was identified by an API 50 CHL kit and N 22's complete sequence of the 16S rDNA sequence. BLASTN analysis of the 16S rDNA sequence revealed a 99% similarity to the 16S rDNA sequence of . Weissella cibaria in the GenBank database. Electron micrographs indicated that the phage head was icosahedral with head size and tail length of 92. ×. 50. nm and 27. nm, respectively. On the basis of the morphology, this phage belongs to the family . Podoviridae. Host-range determination revealed that the phage . Φ 22 was not capable of infecting the other 40 isolates of LAB and referenced . Weissella strains used. A one-step growth experiment showed that the latent period and burst size were estimated at 110. min and 55 phage particles/infected cell, respectively. Furthermore, the phage was infective over a wide range of pH (pH 5.0-8.0) and the . D time of . Φ 22 was calculated as 88. s at 70. °C and 15. s at 80. °C. Phage titers decreased below the detection limit (20. PFU/ml) after heating for more than 60. s at 80. °C, or 20. s at 90. °C or less than 10. s at 100. °C. The results from the study of Nham revealed that . Φ 22 was active against the potential starter culture (. W. cibaria N 22) for Nham fermentation. Phage infection could adversely affect the fermentation process of Nham by delaying acidification when using . W. cibaria N 22 as a starter. However, the results from a sensory test revealed that the panelists did not detect any defects in the final products. This is the first report on the isolation of . W. cibaria phage. © 2010 Elsevier Ltd.