The blue discoloration in Mozzarella cheese comes from bacterial spoilage due to contamination with Pseudomonas. Fourteen Pseudomonas fluorescens strains from international collections and 55 new isolates of dominant bacterial populations from spoiled fresh cheese samples were examined to assess genotypic and phenotypic strain diversity. Isolates were identified by 16S rRNA gene sequencing and tested for the production of the blue pigment at various temperatures on Mascarpone agar and in Mozzarella preserving fluid (the salty water in which the cheese is conserved, which becomes enriched by cheese minerals and peptides during storage). Pulsed-field gel electrophoresis analysis after treatment with the endonuclease SpeI separated the isolates into 42 genotypes at a similarity level of 80%. Based on the pulsotype clustering, 12 representative strains producing the blue discoloration were chosen for the multilocus sequence typing targeting the gyrB, glnS, ileS, nuoD, recA, rpoB, and rpoD genes. Four new sequence typing profiles were discovered, and the concatenated sequences of the investigated loci grouped the tested strains into the so-called "blue branch" of the P. fluorescens phylogenetic tree, confirming the linkage between pigment production and a specific genomic cluster. Growth temperature affected pigment production; the blue discoloration appeared at 4 and 14°C but not at 30°C. Similarly, the carbon source influenced the phenomenon; the blue phenotype was generated in the presence of glucose but not in the presence of galactose, sodium succinate, sodium citrate, or sodium lactate.

Strain diversity of pseudomonas fluorescens group with potential blue pigment phenotype isolated from dairy products / M. Chierici, C. Picozzi, M.G. La Spina, C. Orsi, I. Vigentini, V. Zambrini, R. Foschino. - In: JOURNAL OF FOOD PROTECTION. - ISSN 0362-028X. - 79:8(2016), pp. 1430-1435. [10.4315/0362-028X.JFP-15-589]

Strain diversity of pseudomonas fluorescens group with potential blue pigment phenotype isolated from dairy products

M. Chierici
Primo
;
C. Picozzi
Secondo
;
I. Vigentini;R. Foschino
2016

Abstract

The blue discoloration in Mozzarella cheese comes from bacterial spoilage due to contamination with Pseudomonas. Fourteen Pseudomonas fluorescens strains from international collections and 55 new isolates of dominant bacterial populations from spoiled fresh cheese samples were examined to assess genotypic and phenotypic strain diversity. Isolates were identified by 16S rRNA gene sequencing and tested for the production of the blue pigment at various temperatures on Mascarpone agar and in Mozzarella preserving fluid (the salty water in which the cheese is conserved, which becomes enriched by cheese minerals and peptides during storage). Pulsed-field gel electrophoresis analysis after treatment with the endonuclease SpeI separated the isolates into 42 genotypes at a similarity level of 80%. Based on the pulsotype clustering, 12 representative strains producing the blue discoloration were chosen for the multilocus sequence typing targeting the gyrB, glnS, ileS, nuoD, recA, rpoB, and rpoD genes. Four new sequence typing profiles were discovered, and the concatenated sequences of the investigated loci grouped the tested strains into the so-called "blue branch" of the P. fluorescens phylogenetic tree, confirming the linkage between pigment production and a specific genomic cluster. Growth temperature affected pigment production; the blue discoloration appeared at 4 and 14°C but not at 30°C. Similarly, the carbon source influenced the phenomenon; the blue phenotype was generated in the presence of glucose but not in the presence of galactose, sodium succinate, sodium citrate, or sodium lactate.
Blue discoloration; Mozzarella cheese spoilage; Multilocus sequence typing; Pseudomonas fluorescens; Pulsed-field; gel electrophoresis; Restriction endonuclease analysis
Settore AGR/16 - Microbiologia Agraria
Article (author)
File in questo prodotto:
File Dimensione Formato  
Chierici_et_al 2016 J Food Prot.pdf

accesso riservato

Tipologia: Publisher's version/PDF
Dimensione 657.36 kB
Formato Adobe PDF
657.36 kB Adobe PDF   Visualizza/Apri   Richiedi una copia
Pubblicazioni consigliate

Caricamento pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/447616
Citazioni
  • ???jsp.display-item.citation.pmc??? 3
  • Scopus 18
  • ???jsp.display-item.citation.isi??? 16
social impact