A representative genomic 16S rRNA sequence of strain MH2T
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 [3
] and the relative frequencies, of taxa and keywords (reduced to their stem [4
]) were determined, weighted by BLAST scores. The most frequently occurring genera were Desulfurella
(10.8%) and Hippea
(8.6%) (44 hits in total). Regarding the single hit to sequences from members of the species, the average identity within HSPs was 99.9%, whereas the average coverage by HSPs was 82.7%. Among all other species, the one yielding the highest score was Desulfurella multipotens
, which corresponded to an identity of 89.6% and an HSP coverage of 82.6%. (Note that the Greengenes database uses the INSDC (= EMBL/NCBI/DDBJ) annotation, which is not an authoritative source for nomenclature or classification.) The highest-scoring environmental sequence was AF232926 ('United Kingdom: Montserrat geothermal springs clone MS10 proteobacterium'), which showed an identity of 88.9% and a HSP coverage of 73.0%. The most frequently occurring keywords within the labels of environmental samples which yielded hits were 'microbi' (5.0%), 'spring' (2.9%), 'sediment' (2.4%), 'soil' (2.3%) and 'industri' (2.2%) (206 hits in total). Environmental samples which yielded hits of a higher score than the highest scoring species were not found.
The 16S rRNA based tree in shows the phylogenetic neighborhood of H. maritima. The sequence of the two identical 16S rRNA genes differs by one nucleotide from the previously published 16S rRNA sequence (Y18292).
Figure 1 Phylogenetic tree highlighting the position of H. maritima relative to the other type strains within the family Desulfurellaceae. The tree was inferred from 1,526 aligned characters [5,6] of the 16S rRNA gene sequence under the maximum likelihood criterion (more ...)
The cells of H. maritima
are short rods ranging from 1-3 x 0.4–0.8 µm ( and ) that occur singly or in pairs [1
]. H. maritima
is motile by one polar flagellum [1
] (not visible in ). Colonies are whitish-gray with diameters up to 0.5 mm [1
]. H. maritima
cultures require 2.5-3% NaCl and 0.02% (w/v) yeast extract for growth [1
]. The temperature range for growth is between 40°C and 65°C, with an optimum at 52–54°C [1
]. Growth was observed over a pH range of 5.7 to 6.5 with an optimum around 6.0 [1
Scanning electron micrograph of H. maritima MH2T
Table 1 Classification and general features of H. maritima MH2T according to the MIGS recommendations .
All H. maritima
strains can grow on molecular hydrogen, acetate, and saturated fatty acids and require elemental sulfur as the only known electron acceptor [1
]. Strain MH3
, isolated from Matupi Harbor, was the only H. maritima
strain growing on ethanol in the presence of elemental sulfur [1
]. Fumarate supported only weak growth for all three known strains [1
], whereas formate, propionate, butyrate, pyruvate, lactate, succinate, glucose, starch, peptone, methanol did not support growth [1
S were the only detected end products [1
No chemotaxonomical data were reported in the initial description of the organism [1
] nor elsewhere, subsequently.