Brucella melitensis

A Microbial Biorealm page on the genus Brucella melitensis

Classification

Higher order taxa

Kingdom: Bacteria

Phylum: Proteobacteria

Class: Alpha Proteobacteria

Order: Rhizobiales

Family: Brucellaceae

Genus: Brucella

Species

Brucella melitensis

Description and significance

Brucella sp. is a small, Gram-negative coccobacillus, which can be grown slowly in vitro, and causes Brucellosis. Brucellosis can be described as a "zoonotic disease that causes systemic symptoms and can involve many organs and tissues." (Sakran et al. 2006). Brucella sp. acts as a pathogen that can induce "abortion and sterility in domestic mammals and chronic infections in humans known as Malta fever." (Zygmunt et al. 2006). These infections could easily be contracted through "consumption of unpasteurized dairy products and occupational contact." (Sakran et al. 2006). Right now, the most frequent organism in Israel is Brucella melitensis.

Genome structure

Electron micrographs of Vero cells located within the perinuclear envelope infected with the remarkably similar B. abortus. From Detilleux et al.

The genome of Brucella melitensis stain 16M was found to have two circular chromosomes in which 3,294,931 base pairs were distributed after being sequenced. Of those two chromosomes, 3918 ORFS (open reading frames) were predicted. It was also discovered that genes that coded for DNA replication, protein synthesis, core metabolism and cell-wall biosynthesis (all of these were considered "housekeeping genes") were located on both chromosomes (DelVecchio et al. 2002).

After sequencing the genomes of Brucella sp., it was discovered that Brucella abortus, Brucella suis 1330, and Brucella melitensis 16M had a genetic content and gene organization that were remarkably similar and identical. On the contrary, a number of insertion and deletion events were also identified in the genomes. Because of these insertion and deletion events that occurred, several fragments that were previously recognized as unique sequences belonging to either Brucella suis or Brucella melitensis were also present in the Brucella abortus genome. Therefore, further analysis of the genome sequence of Brucella abortus can give exquisite information of these bacteria. (Halling et al. 2005).

Cell structure and metabolism

Brucella is a Gram-negative pathogen that adapts to an intracellular lifestyle. Experiments suggested that in Brucella melitensis strains, the structure of the bacterium may look either smooth or rough due to the expression of a fatty tissue called O-polysaccharides (OPS) on the outer membrane of the bacterium (Fernandez-Prada et al. 2006). This layer is important in identifying whether a pattern species-specific flagellar gene inactivations and flagellum gene clusters exist, because this would give a better understanding of host specificity and virulence. The need for these species to survive in a species-specific environment provides an explanation that the adaptation of Brucella requires an "intracellular life-style in a protected and more stable local environment or niche that provides a constant supply of nutrients." (Chain et al. 2005).

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Brucella melitensis is one of the six species that causes Brucellosis, which can be described as a fatal zoonotic disease that affects multiple body systems. B. melitensis was originally found as a pathogen that mainly affects goats and sheep but there has been more recent cases where this species has also been a highly pathogenic cause of human brucellosis. Brucellosis is common in many parts of the world, but is rare in the United States. This disease is mainly caused by the transfer of bacteria from farm animals to humans, usually through unpasteurized, contaminated goat milk, in which the bacteria can localize itself intracellularly once inside a host. (Rajashekara et al. 2006). People can become infected through ingestion, inhalation, or direct contact.

Symptoms in Human Brucellosis include:

• Anorexia
• Back pain
• Headache (cephalgia)
• Fatigue
• Fever
• Muscle pain (myalgia)
• Sweating
• Weight loss
• Feeling of general discomfort or uneasiness (often one of the first indications of an infection or disease)

B. melitensis increases its survival and replication in phagocytic cells by minimizing the activation of the defense system of the host. This bacteria is also known for its macrophage infections. Macrophage function is responsible for many pathways important in apoptosis. Because apoptosis kills off infected cells to prevent the spread of infection, disruption in these pathways allows for pathogen survival. (Rajashekara et al. 2006).

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

References

1. Chain P.S., Comerci D.J., Tolmasky M.E., Larimer F.W., Malfatti S.A., Verquez L.M., Aquero F., Land M.L., Ugalde R.A., Garcia E. 2005. "Whole-genome analyses of speciation events in pathogenic Brucellae". Infection and Immunity. 2005 December, 73(12): 8353-8361.

2. DelVecchio V., Kapatral P., Elzer G., Patra C.V., Mujer. 2002. "The genome of Brucella melitensis". Veterinary Microbiology. Volume 90, Issues 1-4, 20 December 2002, Pages 587-592.

3. Fernandez-Prada C.M., Zelazowska E.B., Bhattacharjee A.K., Nikolich M.P., Hoover D.L. 2006. "Identification of smooth and rough forms in cultures of Brucella melitensis strains by flow cytometry". Journal Immunology Methods. 2006 August 31 315(1-2):162-70.

4. Rajashekara G., Eskra L., Mathison A., Petersen E., Yu Q., Harms J., Splitter G. 2006. "Brucella: functional genomics and host-pathogen interactions". Cambridge Journals. Volume 7, Issue 1-2, 2006 December.

Edited by Kathleen Wong