Functional Grouping of Thermophilic Bacillus Strains Using Amplification Profiles of the 16S–23S Internal Spacer Region

Flint, Steve; Ward, Lawrence J. H.; Walker, Kylie

doi:10.1078/0723-2020-00081

Cited by 33 publications

(45 citation statements)

References 15 publications

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“…In the current study, we sequenced two variable regions of the rpoB gene of 6 isolates and found Ͼ99% identity with both G. thermoleovorans and G. stearothermophilus. This is in agreement with previous research, which suggested that these two species are predominant in milk powder manufacturing plants (11). The comparison of the Simpson's index of diversity between the different typing techniques revealed that MLV-HRMA provided a greater level of discrimination than RAPD-PCR while only a small improvement compared to the gel-based analysis of the same amplicons in MLVA.…”

Section: Discussionsupporting

confidence: 91%

“…While not pathogenic, the presence of these heat-stable spores can result in spoilage of reconstituted milk. Recent studies have focused on identifying the predominant spore-forming species within dairy plants (11) and understanding spore adhesion to surfaces (28,36) and subsequent biofilm development within a dairy plant (27,35). However, to date, there has been a lack of a discriminatory and reproducible genotyping assay to track individual strains of Geobacillus spp.…”

mentioning

confidence: 99%

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Genotyping of Present-Day and Historical Geobacillus Species Isolates from Milk Powders by High-Resolution Melt Analysis of Multiple Variable-Number Tandem-Repeat Loci

Seale

Dhakal

Chauhan

et al. 2012

Appl Environ Microbiol

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Section: Discussionsupporting

confidence: 91%

mentioning

confidence: 99%

Genotyping of Present-Day and Historical Geobacillus Species Isolates from Milk Powders by High-Resolution Melt Analysis of Multiple Variable-Number Tandem-Repeat Loci

Seale

Dhakal

Chauhan

et al. 2012

Appl Environ Microbiol

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“…Isolates were identified using species-specific primers for Geobacillus spp. and randomized amplified polymorphic DNA as described by Flint et al (14).…”

Section: Methodsmentioning

confidence: 99%

Recovery of Spores from Thermophilic Dairy Bacilli and Effects of Their Surface Characteristics on Attachment to Different Surfaces

Seale

Flint

McQuillan

et al. 2008

Appl Environ Microbiol

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Spores from four Geobacillus spp. were isolated from a milk powder manufacturing line in New Zealand. Liquid sporulation media produced spore yields of ϳ10 7 spores ml ؊1 ; spores were purified using a two-phase system created with polyethylene glycol 4000 and 3 M phosphate buffer. The zeta potentials of the spores from the four isolates ranged from ؊10 to ؊20 mV at neutral pH, with an isoelectric point between pH 3 and 4. Through contact angle measurements, spores were found to be hydrophilic and had relative hydrophobicity values of 10 to 40%, as measured by the microbial adhesion to hexadecane assay. The most hydrophilic spore isolate with the smallest negative charge attached in the highest numbers to Thermanox and stainless steel (1 ؋ 10 4 spores cm ؊2 ), with fewer spores attaching to glass (3 ؋ 10 3 spores cm ؊2 ). However, spores produced by the other three strains attached in similar numbers (P > 0.05) to all substrata (ϳ1 ؋ 10 3 spores cm ؊2), indicating that there was no simple relationship between individual physicochemical interactions and spore adherence. Therefore, surface modifications which limit the attachment of one strain may not be effective for all stains, and control regimens need to be devised with reference to the characteristics of the particular strains of concern.The presence of spores of thermophilic bacilli are a common problem during milk powder manufacture (32). Thermophilic spores from bacteria such as Geobacillus spp. are normally present in low numbers in the raw milk (31). However, high numbers are often found in the milk powder. The source of these spores is believed to be thermophilic bacteria growing on the surfaces within the heat exchangers and evaporators (43). Biofilms are formed when spores present in the raw milk survive pasteurization, adhere to stainless steel surfaces, and germinate when and where conditions are suitable. As the biofilm matures, cells and spores can slough off and contaminate the product flowing past (13). Spore concentrations as high as 10 5 spores g Ϫ1 can occur in milk powder, resulting in it being downgraded to a lower-value product. As established biofilms are difficult to eradicate (20), prevention of the initial attachment is an alternative approach to control biofilm formation. The initial attachment of microorganisms, including spores, to surfaces is due to physicochemical interactions between their surfaces and the substratum, which are described by the extended Derjaguin, Landau, Verwey, and Overbeek theory (53). Such forces include Lifshitz-van der Waal's, acid/base, and electrostatic interactions. An improved understanding of the interactions that impact spore attachment may help in the development of strategies to reduce spore adherence.Several studies have used electron microscopy and atomic force microscopy to examine the physical structure of the spore's surface (7,18,28). However there have been few studies of the surface chemistry of spores, and it is likely that what little information is known may not be broadly applicable acro...

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“…An aerobic plate count at 55 • C is generally used to quantify thermophilic bacilli in milk products, but in fact this method comprises two distinct categories: obligate thermophiles, which grow at approximately 40 to 68 • C (e.g., Anoxybacillus flavithermus and Geobacillus spp.) (Flint et al, 2001;Ronimus et al, 2003), and facultative thermophiles, which can grow at thermophilic or mesophilic temperatures. Thermophilic bacilli are important hygiene indicators, because they can form endospores and biofilms, and they also contribute to spoilage of dairy products.…”

Section: Milk and Dairy Productsmentioning

confidence: 99%

The Role of Extremophilic Microorganisms and their Bioproducts in Food Processing and Production

Irwin

2012

Extremophiles

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Functional Grouping of Thermophilic Bacillus Strains Using Amplification Profiles of the 16S–23S Internal Spacer Region

Cited by 33 publications

References 15 publications

Genotyping of Present-Day and Historical Geobacillus Species Isolates from Milk Powders by High-Resolution Melt Analysis of Multiple Variable-Number Tandem-Repeat Loci

Genotyping of Present-Day and Historical Geobacillus Species Isolates from Milk Powders by High-Resolution Melt Analysis of Multiple Variable-Number Tandem-Repeat Loci

Recovery of Spores from Thermophilic Dairy Bacilli and Effects of Their Surface Characteristics on Attachment to Different Surfaces

The Role of Extremophilic Microorganisms and their Bioproducts in Food Processing and Production

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