Planococcus halocryophilus; growth in subzero halophilic conditions: Difference between revisions

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Include some current research, with at least one figure showing data.<br>
Include some current research, with at least one figure showing data.<br>
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The <i>P. halocryophilus</i> genome is made up of 35 contiguous strands, composed in a total of 3,428,475 base pairs, with a content of G+C base pairing is at 40.5%. The genome is made up of 85.1% coding bases, of which 53.3% is coding positive strand and the other 46.7% codes negative strand. Figure 3 presents a pie chart for the distribution of genes in correspondence to specific functions. The orthologous groups presented that are related to cellular metabolism show a balanced distribution of about 5% of the total genome. The discernable exception comes from amino acid transport and metabolism, a functional category which makes up roughly 10% of the total genome, the largest orthologous group cluster accounted for with known function. The ratios from Figure 3 present closely comparable results to the genomic classifications of other cryophiles such as P. ingrahamii, E. sibiricum, and P. arcticus.
<br><br>The phylogenetic position of <i>P. halocryophilus</i> was determined by a 16S rRNA gene sequence (amounting to 1550 base pairs) amplified by PCR. This determined that OR1 would be designated with the genus <i>Planococcus</i> and affiliated with the <i>Planomicrobium</i> clade. The <i>P. halocryophilus</i> strain’s location was identified by homologous signature nucleotides to the <i>Planococcus</i> genus, however the strain showed slight varying of clustering patterns compared to that of the <i>Planomicrobium</i> clade. The 16S rRNA genome sequence showed greatest relation to <i>P. dorghaensis</i> (99.6%) and <i>P. antarcticus</i> (98.8%) out of all the <i>Planococcus</i>  species, and the greatest separation from <i>P. columbae</i>  (96.4%). In order for two organisms to be defined as part of the same species, the threshold of comparison is designated as greater than or equal to 70% similarity by DNA-DNA comparison. Upon comparing DNA sequences of <i>P. halocryophilus</i> to that of <i>P. dorghaensis</i>, the similarity was measured at 46%, and for <i>P. antarcticus</i> at 18.2% similarity. These DNA similarity measurements provided concrete evidence that OR1 was an independent species from other <i>Planococcus</i> strains. Figure 4 shows a phylogenetic tree related to 16S RNA gene sequences among related taxa of <i>Planococcus</i> and <i>Planomicrobium</i>.
<br><br><i>P. halocryophilus</i> contain many genomic adaptations to both cold and osmotic stress through proteins that function in response to stress from cold temperatures, high salinity, and general stress. The wide array of proteins creates mechanisms of regulation and repair, act as chaperones, and function as shock proteins. These proteins are encoded by roughly 90 known loci of the OR1 strand genome. 43 loci account for proteins that respond to osmotic stress and adaptation to high salt conditions. Nine loci account for proteins that protect and repair translational factors. Eight loci account for proteins that function in membrane and cell envelope alteration. Seven loci account for proteins stat function as sigma factors. Six loci account for proteins that are involved with DNA replication and repair. Five loci account for cold shock proteins. Finally, there are 11 loci that account for proteins that respond to miscellaneous stress factors, one of which is an SOS-response repressor. These loci provide 90 examples of how cryophiles like <i>P. halocryophilus</i> are able to survive and thrive in harsh subzero saline environments.
<br><br>In order to maintain critical functions within transcription, translation, and regulation, <i>P. halocryophilus</i> contains specific cold-adapted proteins, observed in many cryophiles and mesophiles, that are able to provide essential functions under both cold and osmotic stress. In DNA/RNA replication, specialized helicases and recombination factors are dependable to drive replication in subzero conditions. Other specialized transcription and translation factor proteins have been observed to maintain functions at low temperature or in osmotic stress, including for transcription termination, translation initiation, elongation, and termination. As an alternative under extreme osmotic and subzero stress conditions, specialized sigma factors can be appointed to maintain signal transduction.
<br><br>Figure 5 illustrates three segments of <i>P. halocryophilus</i>, (a) containing adaptive traits encoded by the genome, (b) representing adaptive mechanisms induced by osmotic stress, and (c) showing adaptive mechanisms induced under subzero stress. This figure functions as visual representation for only some of the many understood adaptive and synergistic traits and mechanisms that <i>P. halocryophilus</i> and other cryophiles must demonstrate and regulate in order to survive in high stress environments.


==Section 4==
==Section 4==

Revision as of 01:02, 29 April 2018

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Planococcus halocryophilus (OR1)

Color-enhanced scanning electron micrograph of the Planococcus halocryophilus bacterium. Credit: N.C.S. Mykytczuk et al., the ISME Journal (7 February 2013) © Nature Publishing Group [1].


By Ethan Hanson



Classification:
Kingdom: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Bacillaes
Family:Planococcaceae
Genus: Planococcus

Species:

Planococcus halocryophilus

Section 1

Planococcus halocryophilus is an aerobic, gram-positive bacterium that is found in arctic permafrost. This extremophile is characterized as both a halophile as well as a "hyper"-psychrophile, thriving in an environment of high salinity as well as an extremely low temperature. This bacterium's reproduction capability is measured at the lowest recorded temperature, measured at -15ºC. Planococcus halocryophilus continues to preserve itself at temperatures as low as -25ºC. The bacterium is accountable for effects of global warming, bringing about sizable CO2 emissions concurrent to melting permafrost. Exobiological research towards this extremophile is resonant owing to its similitude of potential target environments for life on Mars as well as Enceladus.

Bacterium Planococcus Halocryophilus Offers Clues about Microbial Life on Enceladus, Mars. www.sci-news.com/space/article01105-planococcus-halocryophilus-bacterium.html.

Color-enhanced scanning electron micrograph of the Planococcus halocryophilus bacterium. Credit: N.C.S. Mykytczuk et al., the ISME Journal (7 February 2013) © Nature Publishing Group [2].
Color-enhanced scanning electron micrograph of the Planococcus halocryophilus bacterium. Credit: N.C.S. Mykytczuk et al., the ISME Journal (7 February 2013) © Nature Publishing Group [3].

Section 2

Include some current research, with at least one figure showing data.

Planococcus halocryophilus (OR1) cells are non-spore forming motile cocci that occur individually or in pairs, with a diameter of 0.8-1.2 micrometers. In colonies, P. halocryophilus appears an opaque, shiny orange color in clusters measured between 2.0-3.0 mm. As stated before, they are gram-positive, aerobic, and both psychrotolerant as well as halotolerant. They can grow at temperatures between -15 and 37ºC, however their optimal temperature of growth is approximately 25ºC. Figure 1 exhibits an Arrhenius plot of log transformed growth rate constants for OR1. Individual measurements come from viable cell count in relation to temperature. Here, the optimal temperature of growth is projected at 25ºC with a maximum 10^8 colony forming units per mL, and a significant drop in growth rate when temperature falls below 10ºC. At <10ºC, the R2 value (slope) increases from approximately 0.49 to approximately 0.94. Growth rate seems to negate below -10ºC.

P. halocryophilus are capable of growth in liquid water of high salinity, up to 19% NaCl, but maintain the ability to grow in conditions of 0% NaCl. When compared to other strains of Planococcus, P. halocryophilus was the only species with a growth temperature range below zero. OR1 also measured out to be the most tolerant to NaCl (ahead of P. maritimus at 17% NaCl). A major physiological feature that distinguishes P. halocryophilus is its transformation of the cellular envelope at temperatures below zero. OR1 cells grown at subzero temperature gain winding nodular sheet encrustations around each individual cell. Its hypothesized that the purpose of this cellular envelope addition is to provide extra protection to the interior of the cell during low-temperature replication. Figure 2 shows three electron microscopic images of P. halocryophilus, (a) and (b) under scanning EM and (c) under transmission EM. Images (a) and (c) show comparison of cell division planes, for cells replicating at 25ºC (a), versus dividing cells at -15ºC (c). The images show dramatic contrast by the nodular cell envelope, showing a 3-dimensional representation of the encrustation in image (c).

P. halocryophilus is an aerobic heterotroph that has the ability to utilize at least 25 different carbon sources (glucose, fructose, galactose, glycerol, rhamnose, mannose, glucosamine, glutamine, maltose, ribose, cellobiose, trehalose, mannitol, lactose, lactic acid, sucrose, gelatin, pectin, dextrin, serine, alanine, arginine, acetic acid, gluconic acid, and glutamic acid), when provided individually.

A cellular fatty acid profile of P. halocryophilus was used to determine which fatty acids were most abundant under specific conditions (control at 25ºC and 0% NaCl) of high salinity and of subzero temperatures separately. Under conditions of high salinity, the most abundant were branched fatty acids and unsaturated fatty acids. Under subzero temperature conditions, the most abundant were straight-chain fatty acids and saturated fatty acids. Very few outliers showed greatest abundance in control conditions. This data is important to membrane fluidity of P. halocryophilus because of the relative abundance of saturated and unsaturated fatty acids. Having more unsaturated fatty acids in conditions of high salinity provides evidence for higher fluidity in the cell membrane, allowing for greater osmotic regulation in ideal temperature conditions. In contrast, the high abundance of saturated fatty acids in subzero conditions provide evidence for lower cell fluidity, in order to protect the cell when metabolic energetics are low due to temperature.

In conditions of cold-specific stress, energy metabolism carries on through increased abundance of substrate shuttling genes and components of the electron transport chain. In subzero conditions (-15ºC), while most metabolic enzymes are repressed, the tricarboxylic cycle and ATP synthase keep the cell alive. In conditions of salt-specific stress, carbohydrate metabolism is extricated by glycogen synthesis, stores induced by specific genes that are activated only under nutrient limited conditions. P. halocryophilus proves its unique resourcefulness from specific response methods through fastidious induction and regulation of metabolic activity.

Color-enhanced scanning electron micrograph of the Planococcus halocryophilus bacterium. Credit: N.C.S. Mykytczuk et al., the ISME Journal (7 February 2013) © Nature Publishing Group [4].

Genome

Include some current research, with at least one figure showing data.

Section 4

Conclusion

References



Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2018, Kenyon College.