Urease biogenesis in Streptococcus thermophilus

Diego Mora*, Christophe Monnet, Carlo Parini, Simone Guglielmetti, Andrea Mariani, Paola Pintus, Francesco Molinari, Daniele Daffonchio, Pier Luigi Manachini

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Urease biogenesis was monitored in the lactic acid bacterium Streptococcus thermophilus during the growth cycle using in-gel detection and a phenol-hypochloride assay. Zymogram analysis, performed in a non-denaturing polyacrylamide gel, enabled visualization of a complex profile of bands whose number and intensity were dependent on the growth phase and culture conditions. The monitoring of urease biogenesis in batch fermentations revealed the onset of enzyme synthesis starting from the mid-exponential growth phase, with a maximum reached during the late exponential phase. Urease activity strongly increased at acidic pH but to a lesser extent when urea and nickel ions were added to the culture medium. When S. thermophilus cells were cultured with pH maintained at a neutral value, urease activity was detectable only in gel with extremely low signals. Evaluation of β-glucuronidase activity in strain DSM 20617 T harboring a transcriptional fusion between a DNA fragment containing the putative urease promoter and the gusA reporter evidenced significant expression at neutral pH that strongly increased in an acidic environment. Further experiments carried out on pureI-gusA recombinant strain revealed that expression of ure genes was not affected by carbohydrates, nickel or urea availability. The presence of consistent expression of ure genes at neutral pH and the absence of induction of expression by carbohydrate availability demonstrated that the transcription of ure genes in S. thermophilus is regulated differently compared with that of the closely related S. salivarius. These differences are discussed taking into consideration the different habitats colonized by the two bacterial species.

Original languageEnglish (US)
Pages (from-to)897-903
Number of pages7
JournalResearch in Microbiology
Issue number9
StatePublished - Nov 2005
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by a grant from the Ministry of the University and Technological and Scientific Research (First 2004). We thank Dr. Giorgio Giraffa (Istituto Speri-mentale Lattiero Caseario di Lodi, Lodi, Italy) for his precious help in total cell protein extraction. We also thank Professor Giovanni Dehò (Dipartimento di Scienze Biomole-colari e Biotechnologie, Università degli Studi di Milano, Milano, Italy) for his helpful suggestions. We are grateful to Michela Besani and Stefania Arioli for their invaluable technical assistance.


  • Expression
  • In-gel detection
  • Streptococcus thermophilus
  • Urease
  • gusA-reporter gene

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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