Abstract
In this essay, a description is done of the Bacteria species Lactobacillus casei and Clostridium botulinum. Their common ground and similarities are presented, being a part of the Low G+C Bacteria, or Firmicutes: Gram-Positive, rod-shaped and fermenters. Additionally, it is also discussed what are their contrasting traits, that keep them distinguished, together with what are the factors used for the various strains’ differentiation, within each species.
Keywords: Lactobacillus casei, Clostridium botulinum, characteristics, similarities, differences, phenotype, structure, phylogenetics.
Low G+C Bacteria – Firmicutes
The Bacteria regarded for this essay are part of the Low G+C Bacteria, or Firmicutes. This name, Low G+C, denominates a phylum of specific Bacteria, which is also called the Firmicutes, which has common history in their evolution process. They are very important, both in industrial and ecological fields.
One of the traits that indentify these Bacteria is being Gram-Positive; meaning that they get stained in purple color when a specific staining process (of Christian Gram) is used. Through this process one can also find another trait: the existence of a thick peptidoglycan wall, a protein and carbohydrate polymer that helps giving the Bacteria structure and shape, together with a function as a protection, preventing osmotic stress to occur. Beneath it these Bacterial have a bilayer of phospholipids with proteins associated that functions as a selective barrier.
The “Low G+C” denomination is related to the fact that these Bacteria’s DNA has a diminished number of G and C bases, when compared to A and T bases. The reproductive system can be through binary fission (Lactobacillus casei) or endospores (Clostridium botulinum). They are also classified by their aerotolerance, or toleration of a certain oxygen level.
Lactobacillus casei and Clostridium botulinum are classified, respectively in the Bacilli Class and Clostridia Class. They have various ways of obtaining the energy they need without oxygen – anaerobic function – being the most common the fermentation.
Lactobacillus casei
Lactobacillus casei makes can be characterized as a rod-shaped, Gram-positive species of Bacteria, which lives in facultative anaerobic environments. It is non-motile, it does not form any spores, the size ranges between 0.7-1.1 x 2.0-4.0 micrometer and they are producers of a substance called lactic acid. For such trait, it is also known as lactic acid bacteria.
Lactobacillus casei has a genome constituted by a circular chromosome and one plasmid, being that in this chromosome one can find 2.9 million pairs of bases and 0.029 in the plasmid. Its strains are classified according to the diverse variability it develops in different niches.
Clostridium botulinum
Clostridium botulinum is a species that is also rod-shaped but this shape also has a slight curve; in opposition to Lactobacillus casei, it is motile and it is found living as Bacteria solely in anaerobic environments (i.e. in environments with low oxygen levels to live and to grow). This species is also different, because it forms spores, which are heat-resistant and have a hard coat; this coat protects them and the essential parts of the bacterium; there are, additionally, several layers of protection membranes; this way, Clostridium botulinum can stay in a dormant stage, for large periods of time (even years).
Clostridium botulinum is a part of the genus Clostridium: Eubacteria with a very diverse phenotype and phylogenetics. When present in the form of spores, if it finds a good anaerobic environment, it will break the spore and develop in the Bacteria form. If the environment in which these bacteria find themselves is poor in the conditions they need, they will form the spores.
This genus has the particularity of providing the Bacteria with larger production of protein toxins. Clostridium botulinum, namely, has its strains classified according to the protein toxin produced.
Conclusion – Comparisons & Contrasts
Regarding these two species of Bacteria – Lactobacillus casei and Clostridium botulinum – similarities can be found in these bacteria, since they both have a rod-shape, they are both Gram-positive with a thick peptidoglycan wall and are both part of the Low G+C, or Firmicutes.
They also have, however, different characteristics: spore formation only happens with Clostridium botulinum; considering the environment type, that Lactobacillus casei is a facultative anaerobic microorganism and, in opposition Clostridium botulinum needs low oxygen levels – anaerobic environments – to live and grow as Bacteria.
On another point of view, these Bacteria species are also differentiated in strains of different characteristics.
Lactobacillus casei’s strains have their differentiation done according to the variability found in relation with the different niches where this bacterium develops. Clostridium botulinum on the other hand, has its different strains differentiated, according to the different types of protein toxins that it produces.
References
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Collins, M.D., East, A.K..Phylogeny and Taxonomy of the Food-borne Pathogen Clostridium botulinum and its Neurotoxins. Retrieved from http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2672.1997.00313.x/abstract
Cornell University: Department of Microbiology. Low G+C Gram-Positive Bacteria. Retrieved from http://micro.cornell.edu/cals/micro/research/labs/angert-lab/low.cfm
H., Cai, Rodriguez, B.T., W, Zhanq, Broadbent, J.R., Steele, J.L..Genotypic and phenotypic characterization of Lactobacillus casei strains isolated from different ecological niches suggests frequent recombination and niche specificity. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/17660430
MicrobeWiki (n.d). Clostridium botulinum. Retrieved from http://microbewiki.kenyon.edu/index.php/Clostridium_botulinum_neu2011#Cell_Structure_and_Metabolism
Wong, Allison (n.d). Lactobacillus casei. Retrieved from http://microbewiki.kenyon.edu/index.php/Lactobacillus_casei
