Complete genome sequence of Cellulophaga algicola type strain (IC166^T)

A representative genomic 16S rRNA sequence of C. algicola was compared using NCBI BLAST under default settings (e.g., considering only the high-scoring segment pairs (HSPs) from the best 250 hits) with the most recent release of the Greengenes database [5] and the relative frequencies, weighted by BLAST scores, of taxa and keywords (reduced to their stem [6]) were determined. The five most frequent genera were Cellulophaga (39.5%), Maribacter (7.8%), Flavobacterium (5.6%), Cytophaga (5.4%) and Formosa (4.7%) (135 hits in total). Regarding the 21 hits to sequences from members of the species, the average identity within HSPs was 95.8%, whereas the average coverage by HSPs was 94.9%. Regarding the 16 hits to sequences from other members of the genus, the average identity within HSPs was 94.7%, whereas the average coverage by HSPs was 94.7%. Among all other species, the one yielding the highest score was C. baltica, which corresponded to an identity of 98.1% and a HSP coverage of 97.8%. The highest-scoring environmental sequence was GU452686 (‘sediments coast oil polluted Black Sea coastal sediment clone 70SZ2’), which showed an identity of 96.5% and a HSP coverage of 98.1%. The five most frequent keywords within the labels of environmental samples which yielded hits were ‘marin’ (4.7%), ‘water’ (4.3%), ‘sediment’ (4.3%), ‘sea’ (3.5%) and ‘coastal’ (2.6%) (115 hits in total). Environmental samples which yielded hits of a higher score than the highest scoring species were not found.

The environmental samples database (env_nt) contains the marine metagenome clone ctg_1101667042524 (AACY022635173) isolated from Sargasso Sea near Bermuda, sharing 92% identity with IC166^T [7] (as of January 2011).

Figure 1 shows the phylogenetic neighborhood of C. algicola IC166^T in a 16S rRNA based tree. The sequences of the five 16S rRNA gene copies in the genome differ from each other by up to two nucleotides, and differ by up to 14 nucleotides from the previously published 16S rRNA sequence (AF001366), which contains nine ambiguous base calls.

The cells of C. algicola are generally rod-shaped with rounded or tapered ends with cell lengths and widths ranging from 1.5 to 4 and 0.4 to 0.5 µm, respectively (Figure 2 and Table 1). C. algicola is motile by gliding [1]. Colonies on marine 2216 agar have yellow-orange pigmentation and a compact center, with a spreading edge possessing lighter pigmentation. Their consistency is slimy and they are slightly sunken into the agar [1]. Flexirubin pigments are not formed. C. algicola grows between 0.5 and 10% NaCl, with the best growth in the presence of about 2% NaCl. The temperature range for growth is between -2°C and 28°C, with an optimum between 15–20°C on solid media and at about 20–25°C in liquid media [1]. The optimal pH for growth is about 7.5 [1].

MIGS ID	Property	Term	Evidence code
	Current classification	Domain Bacteria	TAS [14]
		Phylum Bacteroidetes	TAS [15,16]
		Class Flavobacteria	TAS [17]
		Order ‘Flavobacteriales’	TAS [15]
		Family Flavobacteriaceae	TAS [18–21]
		Genus Cellulophaga	TAS [2]
		Species Cellulophaga algicola	TAS [1]
		Type strain IC166	TAS [1]
	Gram stain	negative	TAS [1]
	Cell shape	rod-shaped	TAS [1]
	Motility	motile by gliding	TAS [1]
	Sporulation	none	TAS [1]
	Temperature range	−2 °C–28°C	TAS [1]
	Optimum temperature	20°C	TAS [1]
	Salinity	0.5–10% NaCl	TAS [1]
MIGS-22	Oxygen requirement	aerobic	TAS [1]
	Carbon source	carbohydrates	TAS [1]
	Energy source	chemoheterotroph	TAS [1]
MIGS-6	Habitat	sea ice diatoms, macrophyte surfaces	TAS [1]
MIGS-15	Biotic relationship	free-living	NAS
MIGS-14	Pathogenicity	none	NAS
	Biosafety level	1	TAS [22]
	Isolation	surfaces of Antarctic algae	TAS [1]
MIGS-4	Geographic location	eastern Antarctic coastal zone	TAS [1]
MIGS-5	Sample collection time	1996	NAS
MIGS-4.1	Latitude	not reported	NAS
MIGS-4.2	Longitude	not reported	NAS
MIGS-4.3	Depth	not reported	NAS
MIGS-4.4	Altitude	not reported	NAS

Evidence codes - IDA: Inferred from Direct Assay (first time in publication); TAS: Traceable Author Statement (i.e., a direct report exists in the literature); NAS: Non-traceable Author Statement (i.e., not directly observed for the living, isolated sample, but based on a generally accepted property for the species, or anecdotal evidence). These evidence codes are from of the Gene Ontology project [23]. If the evidence code is IDA, then the property was directly observed by one of the authors or an expert mentioned in the acknowledgements.

The organism is strictly aerobic and chemoorganotrophic [1]. C. algicola can hydrolyze agar, starch, gelatine, carboxymethylcellulose (CMC), casein, Tween 80, tributyrin and L-tyrosine, but not urate, xanthine or dextran, when grown in presence of 1% L-tyrosine a reddish-brown diffusible pigment is formed [1]. Nitrate reduction is positive, whereas denitrification, H₂S production and indole production are negative [1,18]. Acid is formed oxidatively from D-galactose, D-glucose, D-fructose, sucrose, cellobiose, lactose and mannitol. Strain IC166^T is sensitive to ampicillin, streptomycin and carbenicillin and shows resistance to tetracycline [3].

A closer look on the genome sequence of strain IC166^T revealed a set of genes which might be responsible for the yellow-orange color of C. algicola cells by encoding enzymes that are involved in the synthesis of carotenoids. Carotenoids are produced by the action of geranylgeranyl pyrophosphate synthase (Celal_1770), phytoene synthase (Celal_2446), phytoene desaturase (Celal_2447), lycopene cyclase (Celal_1771) and carotene hydroxylase (Celal_2445). Geranylgeranyl pyrophosphate synthases start the biosynthesis of carotenoids by combining farnesyl pyrophosphate with C₅ isoprenoid units to C₂₀-molecules, geranylgeranyl pyrophosphate. The phytoene synthase catalyzes the condensation of two geranylgeranyl pyrophosphate molecules followed by the removal of diphosphate and a proton shift leading to the formation of phytoene. Sequential desaturation steps are conducted by the phytoene desaturase followed by cyclisation of the ends of the molecules catalyzed by the lycopene cyclase [36].

Strain IC166^T produces a wide range of extracellular enzymes degrading proteins and polysaccharides. These enzymes are cold adapted, they have temperature optima between 15–30°C and can tolerate temperatures below 0°C [37]. For that reason they are of special interest for industrial and biotechnical applications. C. algicola like the other members of the genus Cellulophaga, cannot hydrolyze filter paper or cellulose in its crystalline form, though they can hydrolyze the soluble cellulose derivative carboxymethylcellulose (CMC). The genome sequence of strain IC166^T revealed the presence of three cellulases (Celal_0025, Celal_2753, Celal_3912), probably responsible for the hydrolysis of CMC. In addition two β-glucosidases (Celal_0470, Celal_1802) were identified in the genome, catalyzing the break down of the glycosidic β-1,4 bond between two glucose molecules in cellobiose.

The IC166^T genome contains 22 genes coding for sulfatases, which are located in close proximity to glycoside hydrolase genes suggesting that sulfated polysaccharides may be used as substrates. α-L-fucoidan could be a substrate, as five α-L-fucosidases (Celal_2459, Celal_2466, Celal_2469, Celal_2470, Celal_2473) are located in close proximity to three sulfatases (Celal_2464, Celal_2468, Celal_2472). Sakai and colleagues report the existence of intracellular α-L-fucosidases and sulfatases, which enable ‘Fucophilus fucoidanolyticus’ to degrade fucoidan [38]. This fucoidan degrading ability could be also shared by Coraliomargarita akajimensis, as the annotation of the genome sequence revealed the existence of 49 sulfatases and twelve α-L-fucosidases [39]. In addition, three β-agarases (Celal_2463, Celal_2494, Celal_3979) were identified, with two of them located in the above mentioned region, which is rich in genes encoding glycoside hydrolases and sulfatases.