Domain: Archaea; Phylum: Euryarchaeota; Class: Haloarchaea; Order: Halobacteriaies; Family: Halobacteriaceae; Genus: Haloarcula
Haloarcula hispanica (strain ATCC 33960)
Description and significance
Haloarcula hispanica was isolated in 1986 in Spain from a solar saltern, and was accepted as a new species in 1989 (Liu et al.,2011). Haloarcula hispanica is often grown in lab to be used to study SH1 virus that infects Haloarcula hispanica. Additionally, many researchers have suggested that H. hispanica be used as a model archaeon for study. This is due to its low restriction activity compared to other members of its family, Halobacteriaceae. Apart from the study of host-virus interactions in saline environments, H. hispanica's metabolic pathways have been studied. H. hispanica has been discovered to possess the ability to produce polyhydroxyalkanoates in nutrient-limiting conditions when carbon is in excess (Ding et al.,2014). PHAs are important for storing carbon and energy. Furthermore, studies have been conducted to map out its sulfur metabolic pathway and discern amino acid biosynthesis.
16S Ribosomal RNA Gene Information
The most similar species to H. hispanica is the member of its genus, Holoarcula marismortui. The 16S rRNA sequences of the two species have more than 99% similarity (Ding et al.,2014).
The strain ATCC 33960 has a genome of 3,890,005 bp consisting of two chromosomes (main chromosome 1 and minichromosome 2) and one megaplasmid (Liu et al., 2011). The G+C content of the genome is greater than 62 percent, and nearly 4, 000 genes are protein-coding (Liu et al.,2011). The genome also codes for 48 tRNAs, and 3 copies of 16S rRNA (Ding et al.,2014). In a comparative analysis with another member of its genus, H. marismortui, the two genomes featured 80 percent of proteins with counterparts in the other organism, while approximately 700 proteins were unique to H. hispanica (Arahal et al.,1996). The N601 strain is similar in length, G+C content, and number of protein-coding genes to ATCC 33960, but differs in that it possesses two plasmids (Ding et al.,2014). Additionally, one clustered regularly interspaced short palindromic repeat (CRISPR) array is identified in N601.
Cell structure and metabolism
The distinguishing characteristic of H. hispanica from other members of its genus are its unique polar lipids. Cell growth occurs in triangle or square-shaped sheets of 65 cells (Juez et al.,1986).
Ecology and Pathogenesis
The genus Haloarcula is salt loving and often found in salt lakes,salty soil, and solar saterns. The genus Haloarcula requires at least 1.5 M NaCl for growth, but grow optimally in 2.0 to 4.5 M NaCl. The optimal temperature for growth is 40-45 degrees Celsius (Liu et al,. 2011).
Current research is being done by Li et al. (2014). They found that to adapt the Haloarcula hispanica CRISPR-Cas system to a purified virus requires a priming process.
Arahal, D. R., Dewhirst, F. E., Paster, B. J., Volcani, B. E., & Ventosa, A. (1996). Phylogenetic analyses of some extremely halophilic archaea isolated from Dead Sea water, determined on the basis of their 16S rRNA sequences. Applied and Environmental Microbiology, 62(10), 3779-3786.
Ding, J. Y., Chiang, P. W., Hong, M. J., Dyall-Smith, M., & Tang, S. L. (2014). Complete genome sequence of the extremely halophilic archaeon Haloarcula hispanica strain N601. Genome announcements, 2(2), e00178-14.
Juez, G., Rodriguez-Valera, F., Ventosa, A., & Kushner, D. J. (1986). Haloarcula hispanica spec. nov. and Haloferax gibbonsii spec, nov., two new species of extremely halophilic archaebacteria. Systematic and Applied Microbiology, 8(1), 75-79.
Li, M., Wang, R., Zhao, D., & Xiang, H. (2014). Adaptation of the Haloarcula hispanica CRISPR-Cas system to a purified virus strictly requires a priming process. Nucleic Acids Research, 42(4), 2483-2492.
Liu, H., Wu, Z., Li, M., Zhang, F., Zheng, H., Han, J., & Xiang, H. (2011). Complete genome sequence of Haloarcula hispanica, a model haloarchaeon for studying genetics, metabolism, and virus-host interaction. Journal of Bacteriology, 193(21), 6086-6087.
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