Evolution of Lactobacillus Bulgaricus and Escherichia Coli - Essay Example

A bacterium is a single-celled organism (a prokaryotic cell) and it is usually smaller than a eukaryotic cell. Prokaryotic cells differ from eukaryotic cells regarding their structure and evolution. However, the prokaryotic cells also differ in their structure and evolution. For instance, there are different shapes of bacteria cells such as rods, spheres, and spirals. Other than the differences in their shapes, some bacteria stain positive (gram-positive bacteria) and others that stain negative (gram-negative bacteria). In this paper, the differences and similarities in the structure and evolution of Lactobacillus bulgaricus and Escherichia coli will be discussed.

Both Escherichia coli and Lactobacillus bulgaricus are bacteria; however, Escherichia coli are gram-negative bacteria and Lactobacillus bulgaricus are gram-positive bacteria. Escherichia coli are gram-negative bacteria, which inhabit the intestines of healthy animals and humans (Canadian Medical Association Journal, 2000). The majority of the Escherichia coli serotypes are not pathogenic; however, those that lead to diseases are grouped and classified based on their pathogenic mechanisms. Presently, there are six Escherichia coli pathotypes known to cause diarrhoea in human beings, and they include enteroinvasive E. coli, enteropathogenic E. coli, enterohaemorrhagic E. coli (EHEC) (Shiga toxin-producing E. coli [STEC]), enterotoxigenic E.coli (ETEC), diffusing adhering E. coli, and enteroaggregative E. coli (Naicker, Olaniran, and Pillay, 2011).

However, pathotypes of E. coli such as ETEC and STEC are potent pathogens linked with mortality and waterborne disease outbreaks in humans (Naicker, Olaniran, and Pillay, 2011). On the other hand, the Lactobacillus delbrueckii subspecies bulgaricus is a gram-positive bacterium, and it is closely associated with L. acidophilus, L. acetotolerans, L. acidophilus, L. gasseri, L. helveticus, and L. amylovorus. The ratio of GC content in L. delbrueckii subsp. bulgaricus is higher (49-51 per cent) than the other species (34 – 46 per cent) in this phylogenetic tree (The Regents of the University of California, 2012).

The structure of both Escherichia coli and Lactobacillus bulgaricus is the same. Both bacteria are rod-shaped, and they are non-spore forming. However, some differences distinguish Escherichia coli from Lactobacillus bulgaricus. Escherichia coli is non-spore-forming rod bacteria. Most of the strains possess peritrichous flagella, fimbriate and motile. A capsule in the form of a mucoid is usually present. They are usually serotyped based on their antigenic structure, that is, they are classified based on their lipopolysaccharide. The lipopolysaccharide O is the somatic antigen, H is the flagellar antigen, and K is the capsular antigen. E. coli have non-flagellar appendages referred to as pills. It is important to note that some rods are flagellated, and others are not but in the case of E. coli, they do not possess flagella. They also possess endotoxins just like the other gram-negative bacteria. Endotoxins are less toxic than exotoxins, and they are generally released in soluble form when the bacteria is growing and freed when the bacteria lyse. It is important to note that particular strains of E. coli produce exotoxins (Nagaraja, 1999).

Lactobacillus delbrueckii subsp. bulgaricus cell is a nonmotile rod with rounded edges. They usually occur singly and in short chains. Lactobacillus bulgaricus generally contain internal granulation demonstration with methylene blue stain, which makes it a gram-positive bacterium. The surface growth of the cell (Lactobacillus bulgaricus) is greatly improved by anaerobiosis or reduced oxygen pressure. They are obligately homofermentative and grow well at a temperature of 45°C (Bergey and Boone, 2009). Other important features of this species are that it is non-spore forming and facultatively anaerobic. The specie is acid tolerant, and it is unable to synthesize porphyrins. It has a strictly fermentative metabolism, and lactic acid is the main metabolic product.