Temporal Stability and Biodiversity of Two Complex Antilisterial Cheese-Ripening Microbial Consortia

Abstract

The temporal stability and diversity of bacterial species composition as well as the antilisterial potential of two different, complex, and undefined microbial consortia from red-smear soft cheeses were investigated. Samples were collected twice, at 6-month intervals, from each of two food producers, and a total of 400 bacterial isolates were identified by Fourier-transform infrared spectroscopy and 16S ribosomal DNA sequence analysis. Coryneform bacteria represented the majority of the isolates, with certain species being predominant. In addition, Marinolactobacillus psychrotolerans, Halomonas venusta, Halomonas variabilis, Halomonas sp. (10 6 to 10 7 CFU per g of smear), and an unknown, gram-positive bacterium (10 7 to 10 8 CFU per g of smear) are described for the first time in such a consortium. The species composition of one consortium was quite stable over 6 months, but the other consortium revealed less diversity of coryneform species as well as less stability. While the first consortium had a stable, extraordinarily high antilisterial potential in situ, the antilisterial activity of the second consortium was lower and decreased with time. The cause for the antilisterial activity of the two consortia remained unknown but is not due to the secretion of soluble, inhibitory substances by the individual components of the consortium. Our data indicate that the stability over time and a potential antilisterial activity are individual characteristics of the ripening consortia which can be monitored and used for safe food production without artificial preservatives.Traditional production of various foodstuffs such as kefir, sourdough, and red-smear cheeses includes the transfer of complex undefined microbial consortia from mature products to freshly prepared matrices. As of now it is not known whether the repeated transfer to fresh substrates, or their indigenous microflora, influences the composition of the respective consortia over time. In the case of red-smear cheeses, the microbial succession during surface ripening starts with the growth of yeasts, which metabolize the lactic acid present and raise the pH on the cheese surface from about 5.0 to about 6.0. When the pH is about 6.0, a salt-tolerant, usually very complex and undefined bacterial consortium begins to develop (8,13,29) and eventually covers the entire surface of the cheese. Despite their complex and undefined composition, analysis of bacterial surface-ripening floras of 19 different smeared cheeses yielded no indication that nonculturable bacteria contribute significantly to these floras (11). Bacterial surface floras consist mainly of a large number of coryneform species (3,4,14,33,37). Identification of coryneform bacteria usually is performed on the basis of physiological, phenotypic, and biochemical characteristics (18,19,24,32,33). These methods, however, do not always provide satisfactory results (5, 27), and they are both too laborious and too time-consuming to be performed on a routine basis. In contrast, molecular methods such as analysi...

Genetic traceability of the geographical origin of typical Italian water buffalo Mozzarella cheese: a preliminary approach

“…Three further samples per brand (sets 2-4) were taken 12 months later and analysed. The obtained band patterns were very similar, although not always identical, to the ones from set 1; their correspondence according to their origin was evident, suggesting the substantial stability of microbial community composition over time, as previously reported for some cheese bacterial communities (Maoz et al 2003). Phylogenetic analyses were performed as above, except for an improved 1000-replicate bootstrapping because of the high number of samples.…”

Emetic toxin formation of Bacillus cereus is restricted to a single evolutionary lineage of closely related strains

“…FTIR is a fast technique that has already been demonstrated to be suitable for classification and identification of microorganisms at the species and subspecies level (e.g. Levier et al, 1997;Oberreuter et al, 2002b;Maoz et al, 2003), as well as for rapid screening of environmental isolates (Tindall et al, 2000). The recently developed MLST scheme for B. cereus (Helgason et al, 2004) is suitable to study the genetic relationship among emetic food-poisoning isolates.…”

Bavariicoccus seileri gen. nov., sp. nov., isolated from the surface and smear water of German red smear soft cheese

“…For the ripening process, the microbial consortia of mature cheeses are washed off the surfaces with a brine solution, which is then used for inoculation of freshly produced cheeses. By virtue of the traditional manufacturing process, a variety of different smear cheeses exist which often comprise quite complex, species-rich microbial consortia (Brennan et al, 2004;Feurer et al, 2004;Maoz et al, 2003;Mounier et al, 2005;Wenning et al, 2006). Some recently described species have been isolated from these consortia, such as Agrococcus casei (Bora et al, 2007), Arthrobacter bergerei and Arthrobacter arilaitensis (Irlinger et al, 2005), Brevibacterium aurantiacum (Gavrish et al, 2004), Corynebacterium casei (Brennan et al, 2001) and Microbacterium gubbeenense (Brennan et al, 2001).…”

“…For the ripening process, the microbial consortia of mature cheeses are washed off the surfaces with a brine solution, which is then used for inoculation of freshly produced cheeses. By virtue of the traditional manufacturing process, a variety of different smear cheeses exist which often comprise quite complex, species-rich microbial consortia (Brennan et al, 2004;Feurer et al, 2004;Maoz et al, 2003; Mounier et al, 2005;Wenning et al, 2006). Some recently described species have been isolated from these consortia, such as We have studied the species composition of South German red smear microbial consortia by aerobic cultivation on PC agar supplemented with 3 % NaCl (Maoz et al, 2003) and quantitative analysis of the species composition by Fouriertransform infrared (FT-IR) spectroscopy.…”

“…We have studied the species composition of South German red smear microbial consortia by aerobic cultivation on PC agar supplemented with 3 % NaCl (Maoz et al, 2003) and quantitative analysis of the species composition by Fouriertransform infrared (FT-IR) spectroscopy. FT-IR sample preparation, spectrum recording and data evaluation were performed as described by Kümmerle et al (1998) using an IFS-28B spectrometer and OPUS version 5.5 (Bruker).…”