Abiotic and Microbiotic Factors Controlling Biofilm Formation by Thermophilic Sporeformers

Abstract

e One of the major concerns in the production of dairy concentrates is the risk of contamination by heat-resistant spores from thermophilic bacteria. In order to acquire more insight in the composition of microbial communities occurring in the dairy concentrate industry, a bar-coded 16S amplicon sequencing analysis was carried out on milk, final products, and fouling samples taken from dairy concentrate production lines. The analysis of these samples revealed the presence of DNA from a broad range of bacterial taxa, including a majority of mesophiles and a minority of (thermophilic) sporeforming bacteria. Enrichments of fouling samples at 55°C showed the accumulation of predominantly Brevibacillus and Bacillus, whereas enrichments at 65°C led to the accumulation of Anoxybacillus and Geobacillus species. Bacterial population analysis of biofilms grown using fouling samples as an inoculum indicated that both Anoxybacillus and Geobacillus preferentially form biofilms on surfaces at air-liquid interfaces rather than on submerged surfaces. Three of the most potent biofilm-forming strains isolated from the dairy factory industrial samples, including Geobacillus thermoglucosidans, Geobacillus stearothermophilus, and Anoxybacillus flavithermus, have been characterized in detail with respect to their growth conditions and spore resistance. Strikingly, Geobacillus thermoglucosidans, which forms the most thermostable spores of these three species, is not able to grow in dairy intermediates as a pure culture but appears to be dependent for growth on other spoilage organisms present, probably as a result of their proteolytic activity. These results underscore the importance of abiotic and microbiotic factors in niche colonization in dairy factories, where the presence of thermophilic sporeformers can affect the quality of end products.

Spores in dairy – new insights in detection, enumeration and risk assessment

“…Figure 2 furthermore indicates the most heat-resistant spores of G. stearothermophilus are not or only slightly reduced upon a UHT treatment at F 0 = 5.3. When plotting spore D-values of various other spore formers encountered in dairy products (B. sporothermodurans (Huemer et al 1998), G. thermoglucosidans (Zhao et al 2013), An. flavithermus (Witthuhn et al 2011) and Bacillus species (Berendsen et al 2015b;2016b)) against the 95% confidence interval of D-values for spores of G. stearothermophilus, it stands out that the heat resistance of spores of some strains Bacillus spp.…”

Shaping the oral microbiota through intimate kissing

“…The DNA extractions were performed using a phenol bead beating procedure as described previously [ 14 ]. Shortly, mechanical disruption of bacterial cells was done by bead beating for 2 minutes in a mini-beadbeater-8 cell disruptor and chromosomal DNA was obtained by binding to and washing from magnetic beads.…”

“…The 454 sequence data were demultiplexed and quality filtered as described by Zhao et al . [ 14 ] using modules implemented in the Mothur software platform [ 17 ]. Aligned 16S rRNA gene sequences were clustered into operational taxonomic units (OTUs), defined by 97% identity, using the average linkage clustering method.…”

Evaluation of a non-submerged cultivation assay combined to ESEM imaging for analysis of biofilms formed by dairy-associated sporeforming bacteria

“…Author(s) agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License bacteria such as Bacillus cereus (Wijman et al, 2007) and the thermophilic Geobacillus or Anoxybacillus (Zhao et al, 2013). Another simple model is the microorganism carrier-surface method previously described by Maris (1992) for testing the effectiveness of sanitizers.…”