The name Acinetobacter comes from the translation of a scientific Greek word, and it means nonmotile/immobile rod.
Members of the genus Acinetobacter are gram-negative, nonmotile, strictly aerobic, oxidase-negative coccobacilli. The bacteria of the genus do not make spores. Acinetobacter species are found in soil and water, sewage, human clinical specimens, and activated sludge. (Yoon et al., 2007).
The genus is known to cause diseases in hospitals, especially in intensive care units.
Colonies of strain A. marinus on marine agar are circular, smooth, glistening, slightly convex, milky-white in color, and 0.8-1.0 mm in diameter after 3 days of incubation at 30˚C. Colonies of strain A. marinus on nutrient agar are circular to slightly irregular, smooth, glistening, raised, cream-colored, and 2.0-4.0 mm in diameter after 3 days of incubation at 30˚C (Yoon, 2007).
Acinetobacter species are found in soil and water, sewage, human clinical specimens, and activated sludge. The bacteria of the genus are capable of long-term survival on human skin and hospital equipment.
A. marinus was found in the Yellow Sea in Korea (Yoon et al., 2006).
Acinetobacter marinus can be grown on marine agar; it has an optimum temperature range of between 30-37 ˚C. Other free-living members of the genus can be grown on either nutrient agar or nutrient broth.
Acinetobacter marinus has an optimum pH level between 6.0-8.0.
Acinetobacter genus bacteria are ubiquitous, free-living, gram-negative, saprophytic bacilli. The members of the genus are also prevalent in the clinical environment, and can be easily isolated from the skin of hospital patients and doctors where they can exist as commensals or pathogens (Towner, 1997).
Acinetobacter can survive for a long time on human skin as well as on hospital equipment. (Towner, 1997). The members of the genus can develop resistance to major groups of antibiotics. Combination therapy is usually required as part of treatment (Bergogne-Bérézin & Towner, 1996).
There have been reported cases of community-acquired diseases cause by the species of the genus Acinetobacter, but those are rare.
Acinetobacter species engage in a symbiotic relationship with different insect species. Acinetobacter genus bacteria inhabit the midgut of the tsetse flies, Glossina palpalis and Glossina pallicera. The complete development of the Stomoxys calcitrans fly larvae requires the presence of Acinetobacter spp. (Soumana et al., 2012).
Acinetobacter are also known to colonize the cadaver of the moth species Galleria mellonella larvae infected by the Steinernema nematode species. The studies also show that the bacteria are associated with the nematode, and do not originate in the insect, since there is no evidence for the presence of Acinetobacter in the digestive gut of the Galleria (Walsh & Webster, 2003).
Diseases and Parasites
The members of the genus Acinetobacter are known to cause a variety of nosocomial, or hospital-acquired infections, which include bacteraemia, secondary meningitis, urinary tract infections, and nosocomial pneumonia, particularly ventilator-associated pneumonia, in intensive care units (Towner, 1997).
A. marinus is not known to cause any diseases in humans or other animals.
Life History and Behavior
The members of the genus Acinetobacter are generally nonmotile. However, Acinetobacter baumannii show twitching motility on Lysogeny broth (LB) agar plates with agar concentrations between 0.2 and 0.4 %. The motility varies depending on the type of agar used (Clemmer et al., 2011).
Evolution and Systematics
Physiology and Cell Biology
Acinetobacter are gram-negative bacteria. They are nonmotile, strictly aerobic, oxidase-negative coccobacilli. A. marinus is a slightly halophilic bacterial strain, which means it prefers environments with high salinities.
In general, Acinetobacter species are known for their antibiotic and multi-drug resistance. However, due to very limited data on the species, there is no information on A. marinus being resistant to any drugs.
A. marinus can grow in the temperature range of 10-40˚C with an optimum temperature between 30 and 37 ˚C.
Molecular Biology and Genetics
The DNA GC content is 44.1%.
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