''Alicyclobacillus'' is a genus of

Gram-variable Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. The name comes ...

rod-shaped Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archae ...

, spore-forming bacteria. The bacteria are able to grow in acidic conditions, while the spores are able to survive typical

pasteurization In food processing, pasteurization (American and British English spelling differences#-ise, -ize (-isation, -ization), also pasteurisation) is a process of food preservation in which packaged foods (e.g., milk and fruit juices) are treated wi ...

procedures.

Overview

''Alicyclobacilli'' are strictly aerobic, acidophilic, mesophilic to thermophilic, soil-dwelling organisms. ''Alicyclobacilli'' are of special interest to the fruit juice canning industry because common pasteurization techniques (92 °C for 10 seconds) do not deactivate the spores; ''Alicyclobacillus'' species can have a D₉₅-value of over 8 minutes (requiring treatment of over 8 minutes at 95 °C to kill 90% of spores). When a product is spoiled by ''Alicyclobacillus'', the juice products develop a disinfectant-like odor and/or flavor (due to

guaiacol Guaiacol () is an organic compound with the formula C6H4(OH)(OCH3). It is a phenolic compound containing a methoxy functional group. Guaiacol appears as a viscous colorless oil, although aged or impure samples are often yellowish. It occurs wid ...

production), but the bacteria do not cause swelling of the package or discoloration of the product, nor is it pathogenic to humans. ''Alicyclobacilli'' have been implicated in spoilages of pear, orange, peach, mango, and white grape juice, fruit juice blends, and tomato products. Not all ''Alicyclobacilli'' produce guaiacol, and thus not all species are of spoilage concern. '' A. consociatus'' and '' A. pohliae'' were originally classified in genus ''Alicyclobacillus'', but were later reclassified into the novel genus ''

Effusibacillus ''Effusibacillus'' is a genus of Gram-positive, rod-shaped, aerobic, spore-forming bacteria. ''Effusibacillus'' was first proposed in 2014 after a strain of bacteria was isolated from the sediment of a freshwater lake. While genetically similar ...

'' in 2014. Most ''Alicyclobacillus'' species optimally grow in the 40-55 °C range. The exceptions include ''A. acidocaldarius'' (65 °C), ''A. aeris'' (30 °C), ''A. disulfidooxidans'' (35 °C), and ''A. ferrooxydans'' (28 °C). ''A. acidocaldarius'' is the most thermotolerant, as is able to grow in temperatures up to 70 °C. ''A. disulfidooxidans'' is the only psychrotroph, being able to grow at 4 °C. Most species can grow in the pH 2.0-6.0 range, and none have been shown to grow above pH 6.5. ''A. disulfidooxidans'' is the most acid-tolerant, and can grow at pH 0.5.

Background

The first ''Alicyclobacillus'' species was isolated in 1967 from hot springs, and was named ''Bacillus acidocaldarius''. However, it was not until 1982 that the organisms were implicated in the spoilage of apple juice. The next outbreak occurred in 1994, and based on

16S rRNA 16S ribosomal RNA (or 16Svedberg, S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as ...

studies, a separate genus was proposed. The genus name derives from ω-alicyclic fatty acids as the major component in the cellular membrane, and to reflect the previous classification as ''

Bacillus ''Bacillus'', from Latin "bacillus", meaning "little staff, wand", is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-sh ...

''. ''A. acidoterrestris'' is considered the most important spoilage species within the genus ''Alicyclobacillus'', but ''A. acidocaldarius,'' ''A. pomorum,'' and ''A. herbarius'' have also been isolated from spoiled product. Soil is a common habitat for species of ''Alicyclobacillus'', and is likely the source for contamination of food products.

Impact

The canning industry works under the assumption that bacterial spores will not germinate at pH values below 4.6, and that acid-tolerant organisms are not very heat resistant. In this case, a low heat pasteurization process is applicable. However, the emergence of ''Alicyclobacillus'' as a spoilage organism has led some researchers to advocate using ''A. acidoterrestris'' as the reference organism to design pasteurization processes for high acid foods, just as the

thermal death time Thermal death time is how long it takes to kill a specific bacterium at a specific temperature. It was originally developed for food canning and has found applications in cosmetics, producing salmonella-free feeds for animals (e.g. poultry) and pha ...

of ''Clostridium botulinum'' was used to design the sterilization process for low acid canned foods. High-pressure processing has been shown to be effective at inactivating ''A. acidoterrestris'' spores in orange juice. One survey of 8556 samples of fruit and vegetable juices found ''Alicyclobacillus'' in 13% of samples, while another study found ''Alicyclobacillus'' in 6% out of 180 samples, and another found the bacteria in 14% out of 75 samples. In

The Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

in 2013, contamination of

raspberry The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...

with ''Alicyclobacillus'' in pasteurized juices led to a public recall after consumers complained about bad taste and odor.Graanoogst, Audrey. (2013-09-19
Contaminated fruit juice Wicky recalled.
NLTimes.nl. Retrieved 2014-05-03.

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclatu ...

(LPSN) and

National Center for Biotechnology Information The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is lo ...

(NCBI)

References

{{Taxonbar, from=Q1417570 Bacillales Bacteria genera Food microbiology

Overview

Background

Impact

Phylogeny

See also

References