The combined effects of pH, NaCl and temperature on growth of cheese ripening cultures of Debaryomyces hansenii and coryneform bacteria

The growth characteristics of five bacteria, Brevibacterium aurantiacum 1-16-58, Corynebacterium casei DPC 5298 T , Corynebacterium variabile DPC 5310, Microbacterium gubbeenense DPC 5286 T , and Staphylococcus saprophyticus 4E61, all of which were isolated from the surface of smear cheese, were studied in complex and chemically defined media. All of the coryneforms, except M. gubbeenense, grew in 12% salt, while B. aurantiacum and S. saprophyticus grew in 15% salt. All five bacteria assimilated lactate in a semisynthetic medium, and none of the coryneform bacteria assimilated lactose. Glucose assimilation was poor, except by S. saprophyticus and C. casei. Five to seven amino acids were assimilated by the coryneforms and 12 by S. saprophyticus. Glutamate, phenylalanine, and proline were utilized by all five bacteria, whereas utilization of serine, threonine, aspartate, histidine, alanine, arginine, leucine, isoleucine, and glycine depended on the organism. Growth of C. casei restarted after addition of glutamate, proline, serine, and lactate at the end of the exponential phase, indicating that these amino acids and lactate can be used as energy sources. Pantothenic acid was essential for the growth of C. casei and M. gubbeenense. Omission of biotin reduced the growth of B. aurantiacum, C. casei, and M. gubbeenense. All of the bacteria contained lactate dehydrogenase activity (with both pyruvate and lactate as substrates) and glutamate pyruvate transaminase activity but not urease activity.Bacterial surface-ripened cheeses are characterized by the development of a viscous, red-orange smear on the surface composed of yeasts, mainly Debaryomyces hansenii and Geotrichum candidum, and gram-positive bacteria such as coryneforms and staphylococci (10). Because of its tolerance to high salt concentrations and low pH, D. hansenii develops first on the cheese, metabolizing lactate to CO 2 and H 2 O and forming alkaline metabolites, such as ammonia, that lead to deacidification of the cheese surface, enabling the growth of the salttolerant but less-acid-tolerant bacteria.Until recently, Brevibacterium linens was considered to be the major component of the surface microflora, and most of the research on smear cheese bacteria has focused on physiological and growth characteristics either in liquid cultures (13,14,31,32), on experimental cheeses in mixed cultures with D. hansenii (25-27), or on cheese agar (30). During the last few years, the microflora of several smear cheeses has been extensively investigated and categorically identified using combinations of phenotypic and genotypic techniques (9,15,29,33,42 (22,33). Recently, S. saprophyticus has been shown to dominate the surface of Gubbeen cheese early in ripening but is then replaced by corynebacteria, particularly C. casei (38).Strains of B. linens and D. hansenii from commercial laboratories are generally inoculated onto the cheese surface early in ripening, but their subsequent recovery during ripening is very low (39) or absent (34), indicating that an adventitious...

Section: Discussionsupporting

confidence: 85%

mentioning

confidence: 99%

Growth Characteristics of Brevibacterium , Corynebacterium , Microbacterium , and Staphylococcus spp. Isolated from Surface-Ripened Cheese

Mounier

Rea

O’Connor³

et al. 2007

“…To our knowledge, all the studies about the growth behavior of microorganisms isolated from cheese have been done on mixed cultures with only two microorganisms, generally a yeast and a bacterium, on cheese agar (24,25) or on curd made under aseptic conditions (4,20,21,29). Despite the fact that such studies provide interesting information on the individual growth characteristics of these organisms and their contribution to ripening, they do not take account of the fact that the cheese microflora is much more diverse and that interactions may exist between the members of these communities.…”

Section: Discussionmentioning

confidence: 99%

Microbial Interactions within a Cheese Microbial Community

Mounier

Monnet

Vallaeys

et al. 2008

221

203

The interactions that occur during the ripening of smear cheeses are not well understood. Yeast-yeast interactions and yeast-bacterium interactions were investigated within a microbial community composed of three yeasts and six bacteria found in cheese. The growth dynamics of this community was precisely described during the ripening of a model cheese, and the Lotka-Volterra model was used to evaluate species interactions. Subsequently, the effects on ecosystem functioning of yeast omissions in the microbial community were evaluated. It was found both in the Lotka-Volterra model and in the omission study that negative interactions occurred between yeasts. Yarrowia lipolytica inhibited mycelial expansion of Geotrichum candidum, whereas Y. lipolytica and G. candidum inhibited Debaryomyces hansenii cell viability during the stationary phase. However, the mechanisms involved in these interactions remain unclear. It was also shown that yeast-bacterium interactions played a significant role in the establishment of this multispecies ecosystem on the cheese surface. Yeasts were key species in bacterial development, but their influences on the bacteria differed. It appeared that the growth of Arthrobacter arilaitensis or Hafnia alvei relied less on a specific yeast function because these species dominated the bacterial flora, regardless of which yeasts were present in the ecosystem. For other bacteria, such as Leucobacter sp. or Brevibacterium aurantiacum, growth relied on a specific yeast, i.e., G. candidum. Furthermore, B. aurantiacum, Corynebacterium casei, and Staphylococcus xylosus showed reduced colonization capacities in comparison with the other bacteria in this model cheese. Bacterium-bacterium interactions could not be clearly identified.

“…To our knowledge, little is known about gene expression in microorganisms in cocultures. Most mixed-culture studies have been limited to a biochemical approach using two (27,28) or, rarely, more microorganisms (1,31). Recently, transcriptomic approaches have been developed to investigate possible interactions between two or three microorganisms (9,17,25), indicating that such alternative approaches could be used to investigate coculture behavior.…”

Section: Discussionmentioning

confidence: 99%

Investigation of Associations of Yarrowia lipolytica , Staphylococcus xylosus , and Lactococcus lactis in Culture as a First Step in Microbial Interaction Analysis

Mansour

Bailly

Landaud

et al. 2009

The interactions that may occur between microorganisms in different ecosystems have not been adequately studied yet. We investigated yeast-bacterium interactions in a synthetic medium using different culture associations involving the yeast Yarrowia lipolytica 1E07 and two bacteria, Staphylococcus xylosus C2a and Lactococcus lactis LD61. The growth and biochemical characteristics of each microorganism in the different culture associations were studied. The expression of genes related to glucose, lactate, and amino acid catabolism was analyzed by reverse transcription followed by quantitative PCR. Our results show that the growth of Y. lipolytica 1E07 is dramatically reduced by the presence of S. xylosus C2a. As a result of a low amino acid concentration in the medium, the expression of Y. lipolytica genes involved in amino acid catabolism was downregulated in the presence of S. xylosus C2a, even when L. lactis was present in the culture. Furthermore, the production of lactate by both bacteria had an impact on the lactate dehydrogenase gene expression of the yeast, which increased up to 30-fold in the three-species culture compared to the Y. lipolytica 1E07 pure culture. S. xylosus C2a growth dramatically decreased in the presence of Y. lipolytica 1E07. The growth of lactic acid bacteria was not affected by the presence of S. xylosus C2a or Y. lipolytica 1E07, although the study of gene expression showed significant variations.