Higher order taxa
Bacteria; Bacteriodetes; Flavobacteria; Flavobacteriales; Flavobacteriaceae; Maribacter (1)
Flavobacteria on average account for 10-30% of bacterial populations within the epipelagic zones of ocean and coastal waters; however, there are some regions in which they account for 70% of the bacterial population. They have also been known to inhabit benthic habits, which are the bottom sediments of water habitats (2). Flavobacteria play an important role in the carbon cycle by assisting in the degradation of organic plant matter such as phytoplankton and algae (2) (3). The Flavobacteriaceae family of bacteria contains 95 known genera with 393 species while 210 type strains in 80 genera are categorized as marine strains (2).
Maribacter are a genus of bacteria within the Flavobacteriaceae family. The genus was first created to categorize marine bacteria that were aerobic, obligatory and used gliding as a form of motility (3). There are eight known species of Maribacter consisting of 57 strains (2). Six of these species are free-living organisms while only two species are involved with green and red algae. Maribacter have been found in marine habitats including algae, seawater, and sea ice from subantarctic regions of Argentina, the Sea of Japan and the Mediterranean Sea (3).
Discovery of Maribacter stanieri
Maribacter stanieri is a species of marine bacteria that was discovered and described in 2009 by Olga I. Nedashkovskaya, Seung Bum Kim, and Valery V. Mikhailov. The species was found in the Sea of Japan (East Sea) during a survey conducted to analyze coastal microbial communities. Two strains of Maribacter stanieri have been identified and named KMM 6025 and KMM 6046, the latter being the type strain. Strain KMM 6025 was obtained from a sample of seawater while strain KMM 6046 was taken from the green alga Ulva fenestrata (3).
Cell Structure and Genome
Maribacter stanieri cells are yellow pigmented, rod-shaped, and Gram-negative. Motility is achieved by gliding. They range in size from 2.4-5.3 µm long and 0.3-0.5 µm wide. Colonies formed on marine agar plates are yellow, circular, and shiny. Colony diameters range from 2-4 mm. The major fatty acids contained within the species are iso-C15 : 1 G, iso-C15 : 0, C15 : 0, iso-C17 : 1ω9c, iso-C17 : 0 3-OH, and C16 : 1ω7c and/or iso-C15 : 0 2-OH (3).
By analyzing the 16S rRNA gene sequence, it has been determined that Maribacter stanieri has 96.3-98.5% sequence similarity to the previously discovered species of Maribacter. The DNA G+C base composition of Maribacter stanieri is 36-37 mol% (3). The only species within the genus Maribacter that has had its genome sequenced is a strain identified as HTCC2170 and thus, the genome size for Maribacter stanieri is not known at this time (4).
Growth and Metabolism
As marine bacteria, almost all of the known species of Maribacter require Na+ ions for growth and Maribacter stanieri is no exception. This particular species can grow in NaCl concentrations of 0.5 to 8% with optimal growth occurring between 0.5 and 2% NaCl. Maribacter stanieri prefers temperatures between 23 and 28 ºC and a pH level of 7.0 to 7.5, although growth can occur anywhere from 4 to 35 ºC and within a pH range of 5.5 to 10.0 (3).
Cells are heterotrophic and aerobic making Maribacter stanieri an important player in the carbon cycle within marine habits. It has been shown that cells consume a wide variety of molecules including L-fucose, D-galactose, D-glucose, D-lactose, maltose, melibiose, cellobiose, raffinose, sucrose, arabinose, mannose, DL-xylose, mannitol, N-acetylglucosamine, malate, gluconate, adipate, and citrate and can decompose aesculin, gelatin, and Tweens 20 and 40. Acid is produced when cells consumes the previously mentioned carbohydrates. Maribacter stanieri cannot consume agar, casein, starch, Tween 80, CM-cellulose, chitin, urea, L-arabinose, N-acetylglucosamine, glycerol, inositol, sorbitol, adonitol or dulcitol. Only certain strains can hydrolyze DNA and L-rhamnose. Another key characteristic of metabolism for these cells is that nitrates are reduced to nitrites. Cells tested weakly positive for acetoin production but negative for H2S and indole (3).
Testing confirms that Maribacter stanieri utilizes many enzymes including oxidase, B-galactosidase, alkaline phosphatase, esterase (C4), esterase lipase (C8), valine arylamidase, leucine arylamidase, trypsin, a-chymotrypsin, naphthol-AS-BI-phosphohydrolase, acid phosphatase, a-galactosidase, a- and B-glucosidase, a-mannosidase, and N-acetyl-B-glucosidase. Enzymes absent from the type strain include lipase (C14), cystine arylamidase, a-fucosidase and B-glucuronidase (3).
Very little data has been found regarding the pathogenic characteristics and behavior of Maribacter stanieri. This could be due to its relatively recent discovery and lack of research done with the bacteria. Antibiotic testing shows that the species is susceptible to several antibiotics including carbenicillin, chloramphenicol, doxycycline, lincomycin, erythromycin, neomycin, oleandomycin, tetracycline, and streptomycin. Cells are resistance to polymixin, ampicillin, benzylpenicillin, kanamycin, and gentamicin (3).
Host: Ulva fenestrata
The KMM 6046 strain of Maribacter stanieri can be found living on a species of green alga identified as Ulva fenestrata, also known as sea lettuce (3). Species of Ulva can be found living in coastal areas all over the world. They are very thin, usually no more than two cell layers thick and can be free floating as a meter long sheet or attached to hard surfaces. Ulva fenestrata can be specifically identified by its visible perforations and small holes unique to this particular species of Ulva (5).
Species of this sea lettuce are said to be opportunistic and when conditions are right the algae can form large blooms or colonies. As the massive collection of sea lettuce dies, the surrounding area including the bottom sediment can be rapidly depleted of oxygen killing aerobic organisms inhabiting the area. It is suspected that nutrient and fertilizer run-off into marine habitats contributes to these blooms and subsequent death of local organisms (5).
As mentioned above, Maribacter stanieri is an aerobic, heterotrophic bacterial species that lives on and consumes sea lettuce. This means that Maribacter stanieri is crucial in the carbon cycle within its marine habitat and one of its most important roles could be consuming and controlling the population of Ulva fenestrata and other marine plant species. It has been shown that Flavobacteria such as Maribacter stanieri are associated with the beginning stages of degradation of organic matter in the North Sea and populations of the bacteria dominate during the initial degradation of phytoplankton blooms (2). Maintaining appropriate levels of Maribacter stanieri and other Flavobacteria could be key to controlling outbreaks of sea lettuce growth and indirectly impacts all organismal life within the habitat by sustaining adequate oxygen levels through participation in the degradation of organic plant matter.
A very small amount of research has been conducted on the newly discovered Maribacter stanieri. While there has been little concluded about this species of bacteria as far as the potential benefit for future studies, it has been suggested that the Maribacter genus can serve as a model organism of heterotrophic, aerobic marine bacteria. It is also suggested that the bacteria’s wide variety of carbohydrate enzymes has potential to be used in further research (2).
 Parte, A. “List of prokaryotic names with standing in nomenclature”. LPSN. 2013.  Hahnke, R. and Harder, J. “Phylogenetic diversity of Flavobacteria isolated from the North Sea on solid media”. Systematic and Applied Microbiology. 2013. Vol. 36, Issue 7. p. 497-504.  Kim, S., Mikhailov, V. and Nedashkovskaya, O. “Maribacter stanieri sp. nov., a marine bacterium of the family Flavobacteriaceae”. International Journal of Systemic and Evolutionary Microbiology. 2010. Vol. 60. p. 214-218.  Cho, J., Giovannoni, S., Jang, Y., Kang, I., Oh, H., Vergin, K. and Yang, S. “Complete Genome Sequence of Strain HTCC2170, a Novel Member of the Genus Maribacter in the Family Flavobacteriaceae”. Journal of Bacteriology. 2011. Vol. 193. p. 303-304.  Holmes, J. “Intertidal Organisms EZ-ID Guides”. Washington State University Extension: Island County: Beach Watchers. 2006.  Amann, R., Barbeyron, T., Carpentier, F., L’Haridon, S., Michel, G. and Schuler, M. “Description of Maribacter forsetii sp. nov., a marine Flavobacteriaceae isolated from North Sea water, and emended description of the genus Maribacter”. International Journal of Systemic and Evolutionary Microbiology. 2008. Vol. 58. p. 790-797.
- Edited by Cameron Seymour, student of Rachel Larsen at the University of Southern Maine.