Archaea vs Bacteria

7 Key excerpts on "Archaea vs Bacteria"

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  eBook - ePub

  Microbial Ecology

  • Larry L. Barton, Diana E. Northup(Authors)
  • 2011(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  In general, bacteria in environmental studies are more diverse than archaea in the same environment, with some exceptions reviewed in Aller and Kemp (2008) (plankton, arsenite-oxidizing acidic thermal springs, subsurface hot springs, and methane-rich sediments of a hydrocarbon seep). Aller and Kemp (2008) speculate that this difference in diversity may be due to how archaea live in the environment, the energetic costs of their metabolism, and their metabolic flexibility, suggesting that many members of the Domain Bacteria are more flexible in less extreme environments. The degree to which archaeal and bacterial species are interlinked within an environment is not known and may shed light on the diversity of these two groups. In addition to possible differences in diversity, there are fundamental cellular and genomic differences, which help to elucidate archaeal evolution.

  2.7 Archaea–Bacteria Differences

  You may have already noticed in the earlier sections that archaea and bacteria show major ecological differences and similarities. They also differ substantially at the cellular and genomic levels. The archaea have been shown to have a chimeric nature. Despite their bacteria-like morphology, they show great similarities to the eukarya in their transcription, translation, DNA repair, RNA polymerase, replication, and basal promoter sequences. A surprise finding was that members of the euryarchaeotal branch of the Archaea domain posses homologs of the eukaryotic histones. One of their fundamental differences from the bacteria is that their cell membranes contain isoprene sidechains that are ether-linked to glycerol. Archaeal cell walls are composed of glycoprotein, protein, and pseudomurein (but not murein), and their anitibiotic sensitivity differs from bacterial antibiotic sensitivity. Some energy metabolism methods are unique to the archaea, such as methanogenesis. Overall, archaeal core housekeeping and metabolic functions are similar to bacterial ones, while their information-processing systems are more eukaryotic (Allers and Mevarech 2005; Schleper et al. 2005).

  2.8 Eukarya: A Changing Picture of Phylogenetic Diversity

  The phylogeny of the eukarya has undergone and is undergoing many revisions based on new discoveries. Previously, several phyla of protists diverged at the base of the tree and several of these protists were believed to lack mitochondria (i.e., amitochondriate). This earlier phylogeny was based on 18S rDNA sequence analysis. New phylogenetic trees, based on other genes and proteins, suggest that these protists were not basal as originally thought, and the eukaryotic phylogeny is currently under revision (Parfrey et al. 2006). New findings now show that these groups, which include eukaryotes such as Giardia (a diplomonad), Trichomonas (a parabasilid), and Encephalitozoon (a microsporidian), have mitochondria-like proteins called mitosomes

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  The New Microbiology

  From Microbiomes to CRISPR

  • Pascale Cossart(Author)
  • 2018(Publication Date)
  • ASM Press

    (Publisher)

  PART I New Concepts in Microbiology Passage contains an image

  CHAPTER 1 Bacteria: Many Friends, Few Enemies

  Bacteria are unicellular living organisms that make up one of the three domains of life: Bacteria, Archaea, and Eukaryota (Fig. 1 ). This model of three branches stemming from a common ancestor was first proposed by Carl Wo-ese in 1977. The absence of a nucleus is one major difference between prokaryotes and eukaryotes. Eukaryota or eukaryotes include animals, plants, fungi, and protozoa, which all have nuclei; bacteria and archaea are prokaryotes and do not have a nucleus. The DNA of prokaryotes is non-membrane bound, unlike in eukaryotes. But do not assume that bacteria are merely small sacks full of disorderly contents. Their “interior” is in fact very well organized.

  Archaea, like bacteria, are unicellular organisms but differ from bacteria in that they have lipids that are not found in bacteria and an ensemble of compounds that are similar to those of eukaryotes, in particular the machinery that regulates gene expression. When they were discovered, archaea were thought to exist only in extreme environments, such as very hot water springs, but we now know that they are present everywhere, including in our gut.

  Figure 1.

  The three large domains of life. Bacteria, Archaea, and Eukaryota have a common ancestor.

  Bacteria are extremely varied and make up the most diverse domain of life. They have been on Earth for billions of years and have evolved to survive in a great variety of conditions. There are more than 11,500 known species of bacteria in more than 2,000 genera (groupings of species). These numbers have so far been based only on gene comparisons, particularly the 16S RNA genes, and they keep rising. Classification methods are changing too. Now that we can compare entire genome sequences, the definition of “species” itself is evolving.

  Bacteria may have different shapes (Fig. 2 ). There are four main categories: cocci, or spheres; bacilli, or rods; spirals; and comma-shaped, or curved bacteria. All bacteria divide, regardless of their shape. One bacterium splits into two, via an asexual reproduction. Nevertheless, genetic material can be exchanged between two bacteria by means of mechanisms described as horizontal gene transfer

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  BIOS Instant Notes in Microbiology

  • Simon Baker, Jane Nicklin, Caroline Griffiths(Authors)
  • 2011(Publication Date)
  • Taylor & Francis

    (Publisher)

  Thermophiles, halophiles, and other extremophilic Archaea are well known, but this kingdom also includes many mesophiles. It is becoming apparent that there is a similar or even greater physiological and biochemical diversity in the Archaea compared with the Bacteria. The phylum CrenarchaeotaMost crenarchaeotes cultured in the laboratory are extremophiles capable of growth above 80°C. The best known examples are Sulfolobus solfataricus and Pyrodictium abyssi, the latter holding the current record for biological growth at high temperature (110°C). The morphology of Pyrodictium spp. is unusual, with disk-shaped cells interconnected by hollow tubes of unknown function (cannulae). The phylum EuryarchaeotaThis phylum of the Archaea includes both mesophiles and extremophiles, most notable among which are the methanogens and Pyrococcus furiosus. The phylum KorarchaeotaSeveral phyla in both the Archaea and the Bacteria have been proposed on the basis of the existence of environmental 16S rRNA sequences. The Korarchaeota have been identified in this way, despite claims that the signature sequences were artifacts. A member of the phylum has now been cultured and its genome sequenced.

  Related topics

  (B1 ) Prokaryotic systematics(B2 ) Identification of Bacteria(B3 ) Inference of phylogeny fromrRNA gene sequence(C7 ) Composition of a typical prokaryotic cell

  (C9 ) Cell division(C10 ) Bacterial flagella and movement(C11 ) Prokaryotes and their environment

  The prokaryotes

  The prokaryotes consist of many thousands of known species, to which some order has been applied with the advent of 16S rRNA sequencing. The resulting phylogenetic tree (Figure 1

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  Microbiology For Dummies

  • Jennifer Stearns, Michael Surette(Authors)
  • 2019(Publication Date)
  • For Dummies

    (Publisher)

  Prokaryote is sort of a misnomer because it’s used to talk about all non-nucleated cells, as opposed to eukaryotes, which have a nucleus and organelles, among other things. Both the Bacteria and the Archaea fall into this category, but they’re more distantly related to one another than are the Archaea and the Eukaryota (the third major domain of life) and so they technically shouldn’t be grouped together. Because the Bacteria and the Archaea have many other similarities, it’s simply more convenient to consider them at the same time in this book. However, archaea and bacteria are fundamentally different from one another in terms of cellular structures and genes, including those used to determine ancestry.

  Making sense of the vast numbers of different species and lifestyles is no easy task. In truth, scientists will be working for many years and there still won’t be a tidy sorted list. With this in mind, we’ve put together a chapter describing the major differences between the different prokaryotes based roughly on how they’re related to one another and how they live.

  Another term for how things are related to one another in the evolutionary sense is phylogeny. Phylogeny is measured by comparing the genetic code in each organism. There are several ways to do this, which are summarized in Chapter 11 .

  There are three domains of life: Bacteria, Archaea, and Eukarya, and within each are several phyla . A phylum is a major evolutionary division that is then divided again as class, then order, then family, then genus, then species. This type of organization is called taxonomic classification and each of these divisions is called a taxonomic rank .

  Kingdom used to be the highest taxonomic rank until recently when the higher rank of domain was added. Kingdom is still an important rank when describing major groups within the domain Eukarya, but it’s less useful for describing the Bacteria and the Archaea domains. For this reason, kingdom isn’t used in this chapter.

  Getting to Know the Bacteria

  Of the two domains of prokaryotes, the Bacteria are the best studied and contain all known prokaryotic pathogens. In reality, only about 1 percent of all bacteria have been studied in any detail and of these only a small proportion cause disease. Some, like Pseudomonas, take the opportunity to colonize humans when their immune system is down, but they aren’t primarily human pathogens thriving mainly as free-living bacteria in soils. Others, like Wolbachia and Mycoplasma, lack a cell wall and cannot live outside a host cell. Figure 12-1

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  Environmental Microbiology

  From Genomes to Biogeochemistry

  • Eugene L. Madsen(Author)
  • 2015(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Dictyostelium) the aggregated cells are termed “pseudoplasmodia”. The cellular slime molds have been extensively studied at the biochemical and genetic level, as a model for understanding cellular differentiation. The ecological impact of slime molds is not well explored (e.g., Landolt et al., 2004). For additional information on slime molds see Margulis et al. (1993), Stephenson and Stempen (1994), Wilkinson et al. (2012), and Hoppe (2013).

  The domain Bacteria

  Bacteria are prokaryotes that are distinctive from Archaea (Figure 5.7 ). The critical distinction is in the 16S rRNA gene sequences. Figure 5.13 shows a photograph representative of the common γ-Proteobacteria, Escherichia coli. Additional phenotypic distinctions include: ester linkages in membrane lipids, muramic acid in cell walls, protein synthesis initiated by formylmethionine tRNA, a single type of four-subunit RNA polymerase, Pribnow box-type promoter structure for transcription of genes, sensitivity to certain protein-synthesis inhibitors (chloroamphenicol, streptomycin, kanamycin), and absence of growth above 100 °C; some members carry out chlorophyll-based photosynthesis (see Table 2.3). As mentioned in Section 5.1 and Table 5.1 , the most recent version of Bergey’s Manual of Systematic ­Bacteriology (Garrity et al., 2005) lists 24 phyla of Bacteria. Descriptions of all 24 phyla appear in the manual and are expanded upon at lower taxonomic levels in other related works (e.g., Brenner et al., 2005; Dworkin et al., 2006; Madigan et al., 2014; Bergey et al., 2012). A complete survey of all 24 phyla is beyond the scope of this chapter; however, descriptions based on Garrity et al. (2005) of the eight bacterial phyla shown in Figure 5.7 appear below. Distinctions between Gram-negative and Gram-positive microorganisms were presented in Box 2.3.

  Figure 5.13

  Scanning electron micrograph of the γ-Proteobacteria, E. coli, grown in culture and adhered to a glass surface. (From Rocky Mountain Laboratories, NIAID, NIH, with permission.)

  Aquifex

  Aquifex/Hydrogenobacter is the deepest and earliest branching phylum of Bacteria. All members are Gram-negative, nonsporulating rods or filaments with optimum growth in the range of 65–85 °C. These are chemolithoautotrophs or chemolithoheterotrophs using H2 , S0 , or as electron donors and O2

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  Wastewater Microbiology

  • Gabriel Bitton(Author)
  • 2011(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  1.5 WEB RESOURCES

  1.6 REVIEW QUESTIONS

  1.7 FURTHER READING

  1.1 INTRODUCTION

  The three domains of life are bacteria , archaea , and eukarya (Fig. 1.1 ; Rising and Reysenbach, 2002; Woese, 1987). Bacteria, along with actinomycetes and cyanobacteria (blue-green algae), belong to the prokaryotes , while fungi, protozoa, algae, plant, and animal cells belong to the eukaryotes or eukarya.

  Figure 1.1 The Tree of Life.

  From Rising and Reysenbach (2002) and Woese (1987).

  Viruses are obligate intracellular parasites that belong to neither of these two groups.

  The main characteristics that distinguish prokaryotes from eukaryotes are the following (Fig. 1.2 ):

  • Eukaryotic cells are generally more complex than prokaryotic cells.
  • DNA is enclosed in a nuclear membrane and is associated with histones and other proteins only in eukaryotes.
  • Organelles are membrane-bound in eukaryotes.
  • Prokaryotes divide by binary fission, whereas eukaryotes divide by mitosis.
  • Some structures are absent in prokaryotes, for example, Golgi complex, endoplasmic reticulum, mitochondria, and chloroplasts.

  Figure 1.2 Prokaryotic and eukaryotic cells.

  Other differences between prokaryotes and eukaryotes are shown in Table 1.1 .

  TABLE 1.1. Comparison of Prokaryotes and Eukaryotes

  Feature	Prokaryotes (Bacteria)	Eukaryotes (1 ungi, Protozoa, Algae, Plants, Animals)
  Cell wall	Present in most prokaryotes (absent in mycoplasma); made of peptidoglycan	Absent in animal; present in plants, algae, and fungi

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  Microbes

  Concepts and Applications

  • Prakash S. Bisen, Mousumi Debnath, G. B. Prasad(Authors)
  • 2012(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  halobacteria), a group of archaea, require at least a 2 M salt concentration and are usually found in saturated solutions (about 36% w/v salts). These are the primary inhabitants of salt lakes, inland seas, and evaporating ponds of seawater, such as the Dead Sea and solar salterns, where they tint the water column and sediments bright colors. In other words, they will most likely perish if they are exposed to anything other than a very high concentration salt conditioned environment. These prokaryotes require salt for growth. The high concentration of NaCl in their environment limits the availability of oxygen for respiration. Their cellular machinery is adapted to high salt concentrations by having charged amino acids on their surfaces, allowing the retention of water molecules around these components. They are heterotrophs that normally respire by aerobic means. Most halophiles are unable to survive outside their high salt native environment. Indeed, many cells are so fragile that when placed in distilled water, they immediately lyse from the change in osmotic conditions.

  Haloarchaea, and particularly, the family Halobacteriaceae are members of the domain Archaea and comprise the majority of the prokaryotic population. There are currently 15 recognized genera in the family. The domain Bacteria (mainly Salinibacter ruber) can comprise up to 25% of the prokaryotic community but comprises more commonly a much lower percentage of the overall population.

  A comparatively wide range of taxa have been isolated from saltern crystallizer ponds, including members of the following genera: Haloferax, Halogeometricum, Halococcus, Haloterrigena, Halorubrum, Haloarcula, and Halobacterium (Oren, 2002). However, the viable counts in these cultivation studies have been small when compared to total counts, and the numerical significance of these isolates has been unclear. Only recently it has become possible to determine the identities and relative abundances of organisms in natural populations, typically using polymerase chain reaction (PCR)-based strategies that target 16S small subunit ribosomal ribonucleic acid (16S rRNA) genes. While comparatively few studies of this type have been performed, results from these suggest that some of the most readily isolated and studied genera may not in fact be significant in the in situ community. This is seen in cases such as the genus Haloarcula, which is estimated to make up less than 0.1% of the in situ community but commonly appears in isolation studies.

  5.6.2. Extreme Thermophiles

  A thermophile is a type of extremophilic organism that thrives at relatively high temperatures, between 45 and 80 °C (113 and 176 °F, respectively). Many thermophiles are archaea. Extreme thermophiles are critters that live in some of the most unwelcoming environments on the planet. Archaea such as Sulfolobus acidocaldarius live in hot springs and geysers where the water temperature can be up to 100 °C and the water is filled with sulfuric acid (Fig. 5.24 ). Chlororflexus aurantiacus can carry out photosynthesis at over 60 °C. Pyrococcus furiosus

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