Legionella cherrii

''Legionella cherrii'' is an aerobic, flagellated, Gram-negative bacterium from the genus ''Legionella''. It was isolated from a heated water sample in Minnesota. ''L. cherrii'' is similar to another ''Legionella'' species, '' L. pneumophila'', and is believed to cause major respiratory problems.

History

Discovery

The bacterium was first discovered in 1982 by R. L. Tyndall and C. B. Duncan, who were a part of D.J. Brenner's team that discovered ten new species of ''Legionella''. The isolation process initiated after collecting water samples and transferring them into guinea pig tissues before plating them onto buffered charcoal yeast extract agar. Afterwards, ''L. cherrii'' strains were cultured around 36 °C in an environment containing 2.5% carbon dioxide.

Etymology

The genus ''Legionella'' is named after the 1976 pneumonia (''Legionella pneumophila'') outbreak at the American Legion convention at the Bellevue-Stratford Hotel in Philadelphia. The genus was previously unknown, but it was established three years later. The specific term ''cherrii'' is derived from the scientist William B. Cherry due to his contributions on the studies of Legionellae.

Characterization and genomics

''Legionella cherrii'' is rod-shaped and considered an oxidase-negative bacterium since it lacks cytochrome c oxidase and does not use oxygen in its electron transport chain. ''L. cherrii'' also has the ability to autofluoresce a bluish-white color which was tested by placing the specimen under a Woods lamp-a mechanism that uses backlight to highlight bacteria-and measured under 366 nm wavelengths. ''L. cherrii'' lacks the ability to reduce nitrate, does not contain a urease, and does not convert D-glucose to acid. However, ''L. cherrii'' can hydrolyze gelatin. When on a yeast extract agar plate, ''L. cherrii'' forms a dissolvable brown pigment containing tyrosine. One or a few flagella aid them in their motility. ''Legionella'' organisms’ dependence on L-cysteine and their unique fatty acids and isoprenoid ubiquinone distinguish them from other aerobic bacteria. Like other ''Legionella'' species, ''L. cherrii'' does not form spores and is an aerobic, Gram-negative bacterium. The genome size was sequenced using Illumina HiSeq 2000 and found to be 3.7 Mb. Scaffold assembly was conducted using whole genome shotgun sequencing and 13 scaffolds were found in the complete genome. The G/C content for this particular species of ''Legionella'' is 38.8 mol%. About 3,111 protein coding genes, four rRNA genes, and 36 tRNA genes were also discovered in the genome.

Ecology

Various strains of ''L. cherrii'' were isolated in different areas in 1982. Strains ORW, ORB, and ORZ were discovered in Minnesota in a heated water sample. Another isolate, SC-65-C3, was found in a potable water stern on the island of St. Croix in the Virgin Islands. ''Legionella'' species are mostly found in freshwater environments. However, various strains of ''Legionella'' can congregate in water filtration systems, air conditioning units, humidifiers, and equipment used to combat respiratory infections.

Phylogeny

To determine previously classified ''Legionella'' species' relatedness to ''L. cherrii'', Brenner et al. hybridized DNA reactions using an ''in vitro'' method with phosphate (³²PO₄). A similar percentage of 94% or higher was found between the four ''L. cherrii'' strains. Reassociation criteria differed between 60 and 75 °C depending on the optimal or stringent growth of the bacteria. None to 0.5% divergence was found in related sequences. ''L. steigerwaltii'' was related to ''L. cherrii'' the most, and exhibited a 67% relatedness percentage. Following ''L. steigerwalti'', ''L. dumofii'' (57%), ''L. anisa'' (56%), ''L. bozemanii'' (51%), and ''L. gormanii'' (47%) showed these levels of similarity. Although ''L. parisiensis'' is an autofluorescent species like ''L. cherrii'', it only had a 24% relatedness to ''L. cherrii''. Compared to other ''Legionella'' species, ''L. cherrii'' is 6-35% related.

Pathogenesis

''Legionella cherrii'' and other ''Legionella'' species are considered to be intracellular bacteria that can cause major respiratory problems in humans. Infection occurs when a human host inhales the organism, which may be carried in humidified air. Distinguishing patients with Legionnaire’s disease is difficult because most are asymptomatic due to Legionnaire’s disease being similar to other types of pneumonia. Although ''L. pneumophila'' is the leading cause of Legionnaire’s disease, other ''Legionella'' species (such as ''L. cherrii'') likely are capable of causing this disease. The cultural growth period for ''Legionellae'' is typically 3–4 days. Lung biopsy or bronchoscopy is not necessary to obtain a clinical isolate from a human patient. Plated acidification or using BCYE agar increases the level of selectivity and allows easier access to collecting a ''Legionella'' sample from an infected human’s sputum. Not much is known on how to treat Legionnaire’s disease, but one way could be to reduce the amount of biofilm production the bacteria create.

References

External links

Type strain of ''Legionella cherrii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase

{{Taxonbar, from=Q16984288

Legionellales