a. Higher order taxa
Higher Order Taxa: Bacteria; Firmicutes; Clostridia; Clostridiales; Clostridiaceae; Clostridium
Species: Clostridium tagluense
2. Description and significance
Clostridium tagluense is a Gram-positive, anaerobic, psychrotolerant bacteria that was first isolated from the permafrost of the Canadian Arctic Archipelago in 2009 . C. tagluense belongs to the loosely defined genus of Clostridium, which is comprised of over one hundred species that are highly diverse both phenotypically and taxonomically . C. tagluense is involved in ‘blown pack’ spoilage (BPS) of vacuum packaged beef [4,5]. C. tagluense can survive under extreme conditions, including temperatures from -40 to 10 degrees Celsius, and it can also form spores, making its growth difficult to control . Due to these properties, C. tagluense contamination of meat processing plants can be potentially disruptive to food and meat packing industries, as it is highly resilient and is known to cause meat spoilage . Also, due to its psychrotolerant nature and strict anaerobic metabolism, C. tagluense is proposed to have potential in industrial applications that involve synthesis of compounds at low-temperatures and production of biofuels .
3. Genome structure
C. tagluense has a high 16S rRNA sequence similarity (92-99%) to the species in Cluster I of Clostridium (Clostridium sensu stricto), which is defined as the representative species of the loosely defined Clostridium genus [2,7,8]. It’s genome hybridizes with less than 52% of other species within Cluster I of Clostridium, indicating that it is a separate species that has significant differences from other species of the genus 2. Cytosine and guanine comprise 31.5% of the genome, close to that of most species in Cluster I Clostridium .
4. Cell structure
Interesting features of cell structure. Can be combined with “metabolic processes”
5. Morphology and Metabolic processes
C. tagluense is a Gram-positive, motile rod-shaped microbe that is found mostly as individual cells or in pairs. Colonies range in size from 1-2 mm in diameter and are convex in shape and off-white in color 2. Its cell wall peptidoglycan consists of meso-diaminopimelic acid 2. Furthermore, its cell membrane is primarily comprised of four types of fatty acids: cis9 dimethyl acetal fatty acid, C16:1 cis9 fatty acid, C16:0 fatty acid, and C14:0 fatty acid. C. tagluense is capable of forming endospores 2 which are resistant to harsh environments and which enable survival of the species under extreme conditions. Recent research has found antifreeze proteins (AFP) present in the cell, which function by binding to ice crystals and preventing further crystal formation by changing the crystalline structure 9. Although more thorough characterization of these proteins remains to be done, it is believed that the presence of these AFPs enables C. tagluense to grow in 0-28 °C by preventing the bacteria from being killed by the formation of ice crystals around its cells 9. Relative to other Clostridia species, C. tagluense utilizes a fairly limited range of carbohydrates, including glucose, fructose, maltose, and trehalose. The bacteria is able to hydrolyze the protein gelatin but not the carbohydrate starch, which distinguishes it from other cluster I species 2. The major fermentable compounds are acetate, butyrate, isobutyrate, and valerate 2. Formate and ethanol are minor products of fermentation, produced at less than 1 mM concentration. H2O and CO2 gases are accumulated during fermentation as well 2. In order to cause BPS, Clostridium tagluense produces large volumes of gas while using various substrates that are available in raw meat 6.
6. Ecology and Pathology
Clostridium tagluense is a psychrotolerant bacteria that grows in a temperature range from 0-28 degrees Celsius [2.] . The microbe creates spherical endospores that allow it to withstand temperatures below freezing. C. tagluense has an optimal pH of 6.5-7.2 and an optimal NaCl concentration of 0-2% [2.] . It is an obligate anaerobe that cannot grow in the presence of oxygen. These properties allow C. tagluense to reside in vacuum-sealed, frozen meat products and deep within permafrost [2.] .
C. tagluense is not known to cause any human infections. Its main impact on human life lies in its ability to infect meat products. The microbe is known to cause blown-pack spoilage of vacuum-sealed and frozen meat [10.] . This type of spoilage is unlikely to cause disease in humans because meat with this spoilage is typically disposed of before consumption [11.] .
Strains of C. tagluense have been isolated from spoilage juices from beef and samples of lamb femur bones [4.] [10.] . The meat spoilage caused by C. tagluense can lead to legal and economic problems for the meat industry [11.] . C. tagluense spores have been found to survive treatment by peroxyacetic acid and the vacuum-sealing and cooling processes of meat packing [12.] . The best method to stop the growth of C. tagluense found is to lower the pH of its environment below levels it can withstand [4.] .
8. Current Research
Despite the fact that C. tagluense was first isolated from the permafrost of the Canadian Arctic Archipelago, increasing evidence indicates that the bacteria may be found in meat processing plants and involved in red-meat spoilage as well . In fact, a study surveying vacuum packed meat spoilage issues across the United Kingdom and in Ireland has found 4 out of 35 vacuum-packed meat samples with 16S rRNA sequence resembling that of C. tagluense . Moreover, studies disagree on the pH range that is required for the growth of C. tagluense. While some cite pH range of 6.0 - 7.2, which is generally outside the normal range of pH of vacuum packed meat of pH 5.5, growth under pH 5.5 has also been reported . This not only highlights that C. tagluense could proliferate in packaged meat if contaminated, but this also indicates that there are still unknowns regarding the growth characteristics of C. tagluense . The majority of current research on Clostridium tagluense primarily focuses on its prevalence and function in red-meat spoilage. Some research focuses on determining which substrates various psychrophilic or psychrotolerant clostridia, including C. tagluense, are able to utilize in order to grow. The microbe’s ability to cause spoilage of red meat is limited by the availability of fermentable substrates at the meat’s surface . More specifically, even though C. tagluense can normally metabolize glucose and glycogen, the microbe’s metabolism ceases when the pH drops below a certain level. It has been suggested that low pH is a likely cause of cessation of growth of C. tagluense, but more studies will need to be conducted in the future to determine the exact pH level that is necessary to inhibit C. tagluense growth . In addition, research also focuses on determining whether C. tagluense is able to utilize substrates such as amino acids or lactate in order to cause blown pack spoilage of red meat .
In addition to research regarding the relevance of C. tagluense to meat spoilage, other research focuses on the potential applications of the antifreeze proteins found in the bacterial cell. These cold-adapted enzymes are being investigated for use in cold-water detergents, as well as for use cleaning polluted arctic soils . These applications of cold-adapted bacteria are relatively new, and thus present an exciting area of potential discovery. Further research needs to be conducted in this regard before C. tagluense can be exploited for industrial or for ecological purposes.
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[2.] Suetin, S. V., Shcherbakova, V. A., Chuvilskaya, N. A., Rivkina, E. M., Suzina, N. E., Lysenko, A. M., & Gilichinsky, D. A. (2009). Clostridium tagluense sp. nov., a psychrotolerant, anaerobic, spore-forming bacterium from permafrost. International Journal of Systematic and Evolutionary Microbiology 59(6): 1421-1426.
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[4.] Yang, X., & Badoni, M. (2013). Substrate utilization during incubation in meat juice medium psychrotolerant clostridia associated with blown pack spoilage. Food Microbiology, 34(2): 400-405.
[5.] Yang, X., Youssef M. K., Gill C. O., Badoni M., Lopez-Campos O. (2014). Effects of meat pH on growth of 11 species of psychrotolerant clostridia on vacuum packaged beef and blown pack spoilage of the product. Food Microbiology. 39: 13-18.
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[9.] Shcherbakova, V., Troshina, O. (2018). Biotechnological perspectives of microorganisms isolated from the Polar Regions. Microbiology Australia. Retrieved from http://microbiology.publish.csiro.au/?paper=MA18042.
[10.] Brightwell, G., & Horváth, K. M. (2018). Molecular discrimination of New Zealand sourced meat spoilage associated psychrotolerant Clostridium species by ARDRA and its comparison with 16s RNA gene sequencing. Meat Science 138: 23-27.
[11.] Dorn-In, S., Schwaiger, K., Springer, C., Barta, L., Ulrich, S., Gareis, M. (2018). Development of a Multiplex qPCR for the Species Identification of Clostridium Estertheticum, C. Frigoriphilum, C. Bowmanii and C. Tagluense-like from Blown Pack Spoilage (BPS) Meats and from Wild Boars. International Journal of Food Microbiology 286: 162–169.
[12.] Cavill, L., Roneteriea-Monterrubio, A., Helps, C., Corry, J. (2011). Detection of cold-tolerant clostridia other than Clostridium estertheticum in raw vacuum-packed chill-stored meat. Food Microbiology 5(28): 957-963.