Halococcus Descriptive Essay

1. Introduction

Halococcus salifodinae BIpT DSM 8989T was obtained as a viable isolate from Permian rock salt deposits of a mine in Bad Ischl, Austria [1,2]. The strain grew optimally at a salinity of 20%–25%, a pH value of 7.4 and at 40 °C. Subsequently, several halococcal strains were isolated from similar sites in England and Germany, which had identical 16S rRNA gene sequences and numerous similar properties as the Bad Ischl strain BIpT [3].

The genus Halococcus [4], emended by Oren et al. [5] currently comprises seven formally described species, which are listed here with their sites of isolation and reference in brackets: Hcc. morrhuae (seawater, saline lakes, salterns and salted products, [6]), Hcc. saccharolyticus (marine salterns, [7]), Hcc. salifodinae (rock salt from mines in Germany and Austria, also from brine in a salt mine in England, [1]), Hcc. dombrowskii (bore core from a salt mine in Austria, [8]), Hcc. hamelinensis (stromatolites of Shark Bay, Hamelin Pool in Western Australia, [9]), Hcc. qingdaonensis (crude sea-salt sample collected near Qingdao in Eastern China, [10]) and Hcc. thailandensis (fermented fish sauce produced in Thailand) [11]. Thus, two species—Hcc. salifodinae and Hcc. dombrowskii - were isolated from Permo-Triassic salt sediments, whereas the other five species can be regarded as inhabitants of hypersaline surface waters or heavily salted products.

A study by Wright [12] using 16S rRNA gene sequences of 61 haloarchaeal taxa, revealed that the mean genetic divergence over all possible pairs of halophilic archaeal 16S rRNA gene sequences was 12.4 ± 0.38%, indicating close relatedness. In comparison, the greatest genetic divergence within methanogenic archaea was 34.2% [12]. Within the halophilic archaea, Halococcus species form an even closer related group (see Figure 1), with 16S rRNA gene sequence similarities of 98.2%–98.7% between Hcc. thailandensis, Hcc. morrhuae, Hcc. qingdaonensis and Hcc. dombrowskii, and somewhat lower similarities of 93.7%–94.1% between Hcc. hamelinensis, Hcc. saccharolyticus and Hcc. salifodinae [11].

Figure 1. Distance-matrix neighbor-joining tree, showing the phylogenetic relationships of Halococcus type strains. The tree is based on an alignment of 16S rRNA gene sequences. Bootstrap values higher than 70 out of 1000 subreplicates are indicated at the respective bifurcations. The tree was constructed using the neighbour-joining method of Saitou and Nei [13]. The bar represents the scale of estimated evolutionary distance (1 % substitutions at any nucleotide) from the point of divergence. Halobacterium noricense was used as an outgroup.

Figure 1. Distance-matrix neighbor-joining tree, showing the phylogenetic relationships of Halococcus type strains. The tree is based on an alignment of 16S rRNA gene sequences. Bootstrap values higher than 70 out of 1000 subreplicates are indicated at the respective bifurcations. The tree was constructed using the neighbour-joining method of Saitou and Nei [13]. The bar represents the scale of estimated evolutionary distance (1 % substitutions at any nucleotide) from the point of divergence. Halobacterium noricense was used as an outgroup.

Our notions on prokaryotic evolution and evolution in general have been shaped by the concept of a molecular clock, which suggests an approximately uniform rate of molecular evolution among species and duplicated proteins over time [14]. Although subject to various criticisms, molecular-clock techniques still remain the only way to infer the timing of gene duplications and speciation events in the absence of fossil or biogeographical records [14]. The concept was applied previously to date the sequence divergences of halophilic archaeal protein-encoding genes, compared to the divergence of homologous non-halophilic eubacterial protein-encoding genes, assuming a point of haloarchaeal species diversion of 600 million years before present [15]. However, modern results from genome sequences revealed a much more complex history of life than can be depicted in bifurcating trees [16]. Widespread horizontal gene transfer—although occurring to different extents—, endosymbioses, gene losses and other processes cause the presence of different molecules with different histories in a species, and members of the same species were found to differ dramatically in gene content, leading to the suggestion of a fuzzy species concept in prokaryotes [16].

Some of these problems and uncertainties might be resolvable when viable microorganisms from well-dated ancient geological sites would be compared on a molecular basis with contemporary species. A crucial issue is the proof that microorganisms from ancient materials, like million year old deep subseafloor sediments, or Permian salt evaporites, are as old as the geological sites from which they were obtained (see [17,18,19] for discussions). The determination of the age of a single average bacterium is not possible with currently available methods, since its mass is only about a picogram. Thus, claims of ancient microorganisms were often dismissed as being due to laboratory contaminations.

Recently, small particles of about 0.4 μm in diameter were imaged by microscopy directly within fluid inclusions of 22,000–34,000 year old salt bore cores and, following successful culturing, identified as haloarchaea [18,20]. Embedding of halophilic microorganisms in fluid inclusions upon formation of salt crystals is well known, and fluid inclusions have been suggested as sites for preservation of microbial life [21,22,23]. In addition, Gramain et al. [24] reported isolation of haloarchaea from well-dated salt bore cores of Pliocene age (5.3 to 1.8 million years). Thus there is a growing body of evidence that haloarchaea survive for great lengths of time [24].

Here we review the properties of coccoid haloarchaea isolated from Permo-Triassic salt sediments, and relate them to those of halococci, which were isolated from surface waters. In addition, new data on Halococcus salifodinae concerning the chemical composition of its cell wall are included as well as DNA-DNA hybridization experiments between several strains of the species. Recently, the first genome sequence of a halococcus, Hcc. hamelinensis 100A6T, became available [25] and therefore information for several genes (phaC synthases; subunit A of the rotary A-ATPase) is examined here for their potential use in delineating the evolution of haloarchaeal cocci.

To write a narrative essay, you’ll need to tell a story (usually about something that happened to you) in such a way that he audience learns a lesson or gains insight.

To write a descriptive essay, you’ll need to describe a person, object, or event so vividly that the reader feels like he/she could reach out and touch it.

Tips for writing effective narrative and descriptive essays:

  • Tell a story about a moment or event that means a lot to you--it will make it easier for you to tell the story in an interesting way!
  • Get right to the action!  Avoid long introductions and lengthy descriptions--especially at the beginning of your narrative.
  • Make sure your story has a point! Describe what you learned from this experience.
  • Use all five of your senses to describe the setting, characters, and the plot of your story. Don't be afraid to tell the story in your own voice.  Nobody wants to read a story that sounds like a textbook!

How to Write Vivid Descriptions

Having trouble describing a person, object, or event for your narrative or descriptive essay?  Try filling out this chart:

What do you smell?

What do you taste?

What do you see?

What do you hear?

What might you touch or feel?

 

 

 

 

 

Remember:  Avoid simply telling us what something looks like--tell us how it tastes, smells, sounds, or feels!

Consider this…

  • Virginia rain smells different from a California drizzle.
  • A mountain breeze feels different from a sea breeze.
  • We hear different things in one spot, depending on the time of day.
  • You can “taste” things you’ve never eaten: how would sunscreen taste?

Using Concrete Details for Narratives

Effective narrative essays allow readers to visualize everything that's happening, in their minds.  One way to make sure that this occurs is to use concrete, rather than abstract, details. 

Concrete Language

Abstract Language

…makes the story or image seem clearer and more real to us.

...makes the story or image difficult to visualize.

…gives us information that we can easily grasp and perhaps empathize with.

…leaves your reader feeling empty, disconnected, and possibly confused.

The word “abstract” might remind you of modern art.  An abstract painting, for example, does not normally contain recognizable objects.  In other words, we can't look at the painting and immediately say "that's a house" or "that's a bowl of fruit."  To the untrained eye, abstract art looks a bit like a child's finger-painting--just brightly colored splotches on a canvas.
Avoid abstract language—it won’t help the reader understand what you're trying to say!

Examples:

Abstract:  It was a nice day. 
Concrete:  The sun was shining and a slight breeze blew across my face. 

Abstract:  I liked writing poems, not essays. 
Concrete:  I liked writing short, rhythmic poems and hated rambling on about my thoughts in those four-page essays. 

Abstract:  Mr. Smith was a great teacher.
Concrete:  Mr. Smith really knew how to help us turn our thoughts into good stories and essays.

Sample Papers - Narration

Sample Papers - Descriptive

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