Lactobacillus delbrueckii

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Lactobacillus delbrueckii
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Scientific classification
Domain: Bacteria Phylum: Firmicutes Class: Bacilli Order: Lactobacillales Family: Lactobacillaceae Genus: Lactobacillus Species: L. delbrueckii

Description and significance

L. delbrueckii is a gram positive bacteria and facultatively anaerobic. It is long, filamentous and non-motile with its cell size ranging between 0.5- 0.8 by 2.0-9.0 millimeters. The environment in which L. delbrueckii thrives the most would be one of relatively low pH, preferring acidic enviornments making them acid tolerant. L. delbrueckii undergoes obligate homofermtentative metabolism which means they are only able to ferment lactose and no other sugar. L. delbrueckii is found in dairy products such as yogurt, milk, and cheese.

In 1905, Stamen Grigoroy, a Bulgarian doctor, discovered L. delbrueckii subspecies bulgaricus to be a true cause for the existence of natural yogurt. This was an important discovery since it led to further discovery of probiotic affects on humans and animals which include improved lactose tolerance and its ability to stimulate immune responses

Genome structure

Lactobacillus delbrueckii has a circular genome and is made up of 1,864,998 nucleotides. It has a GC content of 49% and has 2,217 genes. Of the 2,217 genes 1,562 code for proteins such as prtB and the lac operon. These proteins contribute to the homofermentative properties observed in L. delbrueckii. The genes that are encoded to take up and break down lactose are the lacS, lacZ, and lac R genes located within the lac operon. Transport of lactose through the membrane is the primary responisibility of lactose permease that is coded by the lacS gene. On the other hand, the lacZ gene, encodes the enzyme B-galactosidase need to metabolize lactose.

Cell structure and metabolism

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Ecology

L. delbrueckii bulgaricus, a subspecie of Lactobacillus delbrueckii is found to have a symbiotic relationship with Streptococcus thermophilus. Together they coexist in starter lactic acid bacteria cultures. The lactic acid that is produced also contributes in preserving milk. L. delbrueckii are also symbiotic with the gastrointestinal tract and vagina of humans.

Pathology

Unlike most microbes, L. delbrueckii is non-pathogenic. It is the source that provides milk, yogurt, cheese, and vegetables.

Application to Biotechnology

Two subspecies of Lactobacillus delbrueckii, L. delbrueckii bulgaricus and L. delbrueckii lactis play a major role in the dairy industry. Fermented yogurt, milk, and cheese are cultured from these two subspecies. If the process of fermentation that occurs through L. delbrueckii bulgaricus and L. delbrueckii lactis came to a halt it would result in a large economic loss. This is why care must be taken to keep the conditions of production constant.

Current Research

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References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

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