Micavibrio

{Uncurated}} A Microbial Biorealm page on the genus Micavibrio

Classification

Higher order taxa

Bacteria; Proteobacteria; Deltaproteobacteria; Bdellovibrionales; Bdellovibrionaceae; Micavibrio

Species

The bacterium Micavibrio aeruginosavorus (yellow), attached to and leeching on a Pseudomonas aeruginosavorus bacterium (purple), surrounded by dead P. aeruginosavorus cells (gray). CREDIT: Martin Wu/Zhang Wang/University of Virginia

M. aeruginosavorus, M. admirandus

Description and significance

Micavibrio aeruginosavorus is a predatory bacteria which displays ‘vampire-like’ behavior in an obligatory parasitic lifestyle on other bacteria. Gram-negative micro-organisms known to be pathogenic in humans, such as Pseudomonas aeruginosa, are the prey for this host specific predator. M. aeruginosavorus' life cycle consists of an attack phase, during which motile M. aeruginosavorus seek their prey, and an attachment phase, during which M. aeruginosavorus attach irreversibly to the cell surfaces of prey bacteria (4). The attached M. aeruginosavorus will feed on their prey and divide by binary fission, which leads to the death of the infected prey cells (4). By coculturing Bdellovibrio bacteriovorus 109J and Micavibrio aeruginosavorus ARL-13 with selected pathogens, [it has been] demonstrated that predatory bacteria are able to attack bacteria from the genus Acinetobacter, Aeromonas, Bordetella, Burkholderia, Citrobacter, Enterobacter, Escherichia, Klebsiella, Listonella, Morganella, Proteus, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio and Yersinia (1). M. aeruginosavorus have an ability to prey and reduce many of the multidrug-resistant pathogens associated with human infection (1). The goal of researchers is to better understand the roles, capabilities, and interactions of M. aeruginosavorus as a potential 'live antibiotic' for the pathogens causing human disease.

Genome structure

The genome of M. aeruginosavorus ARL-13 has been completely sequenced and is 2,481,983 bp long on a single circular molecule with a G+C content of 54% (4). 90.3% of the genome is predicted to code for 2,434 open-reading frames, 40 tRNA genes and one rRNA operon (4). No extragenomic DNA molecules (phage or plasmid) were identified from the sequence and there was a complete absence of mobile genetic elements including insertion sequences, transposons and retrotransposons (4). Nine genomic islands encode multiple genes important for predator-prey interaction (hemolysin-related proteins) (4). RNA-Seq analysis has shown a substantial difference in transcriptome between the attack phase (seeking prey) and attachment phase (feeding on prey and replicating) (4). M. aeruginosavorus encodes six hemolysin related proteins belonging to the RTX family of toxins (following secretion, hemolysin inserts into the host cell membrane, forms a transmembrane pore then lyses the host cell) (4). The genome of M. aeruginosavorus is moderate in size, at 2.4 Mbp, it is almost twice the size of most obligate intracellular alpha-proteobacteria (4). It is substantially smaller than most free-living alpha-proteobacteria, and about 35% smaller than B. bacteriovorus HD100, which is 3.7 Mbp (4). The genome also encodes an impressive selection of hydrolytic enzymes with 4.3% of the genome predicting to encode 49 peptidases and proteases, 12 lipases, 4 RNAses, 2 DNAses and 37 additional hydrolases (4).

Cell and colony structure

Micavibrio aeruginosavorus was first isolated in wastewater. Micavibrio belongs to the alpha subgroup of proteobacteria; they are small (0.5 to 1.5 μm long), rod shaped, and curved and have a single polar flagellum (2). Replication is via binary fission, producing one daughter cell at a time. Micavibrio will form plaques in diluted nutrient broth agar.

Metabolism

Despite being an obligate predator depending on prey for replication, M. aeruginosavorus encodes almost all major metabolic pathways (4). Genome analysis suggests that there are multiple amino acids that it can neither make nor import directly from the environment, thus providing a simple explanation for its strict dependence on prey (4). Genome analysis also show many free-living bacterium features such as genes involved in lipopolysaccharide and cell wall biosynthesis, glycolysis, TCA cycle, electron transport chain, ATP synthase (indication of ATP generation), respiration systems (4). It also contains a pentose phosphate pathway and a full set of genes for the metabolism of nucleotides (4). Micavibrio aeruginosavorus encodes genes for the synthesis of 13 amino acids necessary for protein synthesis but is missing the biosynthesis pathways for the remaining 7 amino acids (Alanine, Arginine, Histidine, Isoleucine, Methionine, Tryptophan and Valine)(4). The genome is also missing transporters for amino acids, peptides and amines, which Micavibrio obtains from its prey(4).

Ecology

Experiments show optimal conditions under which Micavibrio aeruginosavorus was able to prey were temperatures ranging from 25 to 37ºC with an aerobic environment (1). Predation was shown to halt under microaerophilic and anaerobic conditions (1).

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors.

References

1. Dashiff, A., Junka, R., Libera, M. and Kadouri, D. (2011), Predation of human pathogens by the predatory bacteria Micavibrio aeruginosavorus and Bdellovibrio bacteriovorus. Journal of Applied Microbiology, 110: 431–444. doi: 10.1111/j.1365-2672.2010.04900.x

2. Dashiff, A., Keeling, T., & Kadouri, D. (2011). Inhibition of predation by Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus via host cell metabolic activity in the presence of carbohydrates. Applied & Environmental Microbiology, 77(7), 2224-2231. doi: 10.1128/.02565-10

3. Kadouri, Daniel, Nel C. Venzon, and George A. O’Toole. Vulnerability of Pathogenic Biofilms to Micavibrio aeruginosavorus. Applied and Environmental Microbiology. 73.2 (2007): 605-14. doi:10.1128/AEM.01893-06

4. Wang, Z.; Kadouri, D. E.; Wu, M. (2011). "Genomic insights into an obligate epibiotic bacterial predator: Micavibrio aeruginosavorus ARL-13". BMC Genomics 12: 453. doi:10.1186/1471-2164-12-453

Edited by Kelly Gordon and Jennifer Willis of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio