Rod Shaped Bacteria

8 Key excerpts on "Rod Shaped Bacteria"

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  eBook - PDF

  Basic Microbiology: A Illustrated Laboratory Manual

  • Khuntia, B K(Authors)
  • 2021(Publication Date)
  • Daya Publishing House

    (Publisher)

  Figure 2.1: Size of bacteria 2. Rod-shaped Bacteria The cylindrical or rod-shaped bacteria are called ‘bacillus’ (plural: bacilli). They are of three shapes as follows. ( a ) Bacillus: They are rod-shaped bacteria. Based on arrangement they are of the following types. ( i ) Bacillus: The rod-shaped bacteria cells, called bacilli, are present as single individuals. ( ii ) Diplobacillus: The bacilli are arranged in pairs. ( iii ) Streptobacillus: The bacilli are arranged in chains, as the cells divide in one plane. ( iv ) Trichomes: The bacilli are arranged in chains with larger area of end-to-end contact between the cells. ( v ) Palisades: The bacilli bend at the points of division following the cell divisions, resulting in a palisade arrangement resembling a picket fence and angular patterns that look like Chinese letters. ( b ) Coccobacillus: These are so short and stumpy that they appear ovoid. They look like coccus and bacillus. ( c ) Vibrios: They are comma-shaped bacteria with less than one This ebook is exclusively for this university only. Cannot be resold/distributed. complete turn or twist in the cell. 3. Spiral Bacteria Unlike the vibrios, which have less than one complete turn or twist in the cell, the spiral bacteria are rod-shaped bacteria, which have more than one twist in the cell. They usually occur singly. They are of two types as follows: ( a ) Spirillum: They have rigid spiral structure. Spirillum with many turns can superficially resemble spirochetes. They do not have outer sheath and endoflagella, but have typical bacterial flagella. ( b ) Spirochetes: They are flexible and can twist and contort their shape. They have outer sheath and endoflagella, but lack typical bacterial flagella. Figure 2.2: Shape and arrangement of bacteria 4. Filamentous Bacteria They are very long thin filament-shaped bacteria. Some of them form branching filaments resulting in a network of filaments called ‘mycelium’.

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  eBook - ePub

  Microbiology and Chemistry for Environmental Scientists and Engineers

  • Jason Birkett, John Lester(Authors)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  3 for the mycoplasmas. In considering the size of bacteria, it is important to remember that the cell dimensions are likely to vary with age and condition of the culture and also that the various techniques listed to stain and fix the cells prior to measurement under the microscope are likely to cause some degree of distortion. Shrinkage of up to 30% may occur in some electron microscopy preparations. Thus, quoted measurements of cellular size should be regarded as approximate rather than actual values.

  The shape and arrangement of bacterial cells can be seen under the light microscope following staining or by phase contrast. There are three basic shapes: spheres, rods and spirals. Variations in both size and shape occur with age and culture conditions, a phenomenon known as pleomorphism. An example is Acinetobacter which is rod-shaped when young but forms pairs of spheres when mature. Spherical-shaped bacteria are called cocci and are identified by their tendency to divide irregularly in several planes. The disposition of the daughter cells gives rise to single cells (cocci), pairs of cells (sarcinae), clusters (staphylococci) and chains (streptococci). Rod-shaped or cylindrical bacteria may be arranged singly, in pairs end to end, in bundles, clusters, chains or in Chinese letter form where the individual rods lie perpendicularly to each other. Rod-shaped bacilli are also identified by the shape of the rod end, which may be square, rounded or sharply pointed. Spiral-shaped bacteria have cells which bend or twist to form curves or helices. Curved bacteria include the vibrios, which form a comma shape. These may be arranged singly, in S forms, semicircles or wavy chains made up of S forms. The spirilla are distinguished by multiple curves or twists and form long helices, of up to 500 μm in the case of Spirochaeta. Examples of these shapes are given in Fig. 2.4

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  eBook - PDF

  An Introduction to Microbiology

  Pharmaceutical Monographs

  • W. B. Hugo, J. B. Stenlake(Authors)
  • 2014(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  Four variants of the rod-shaped form are found : rods with one convolution (Vibrio), rods with several convolutions (Spirillum), rods which tend to form chains with the cells arranged end to end (some lactobacilli) and those that may show branched forms as seen amongst some of the Actinomycetales. Variants of the coccoid form depend on the degree and manner of aggregation of the cells 1 (a) (b) (c) (d) ^) (/) (g) (//) F I G . 1. Electron micrographs of bacteria to illustrate shape and size. (Upjohn Ltd., Crawley, England, and Kalamazoo, U.S.A.) (a) Staphylococcus aureus (single cell) x 25,000. (b) Neisseria gonorrheae x 30,000. (c) Clostridium perfringens (welchii) dividing cells x 25,000. (d) Diplococcus pneumoniae x 35,000. (e) Aerobacter aerogenes x 30,000. (/) Salmonella schottmülleri (paratyphi) x 25,000. (g) Streptococcus viridans x 30,000. (h) Corynebacterium diphtheriae x 25,000. THE BACTERIAL CELL after division during reproduction. Coccoid forms may occur singly, as pairs (diplococci), as cubical aggregates of the sphere (sarcinae), in irregular clusters, often likened to a bunch of grapes (staphylococci) or in chains (streptococci). Amongst some species, for example Leuconostoc, ovoid cells are found. Much use has been made of cellular morphology in evolving systems of bacterial classification (Chapter 4). Micrographs of bacteria are shown in Figs. 1 and 2. FIG. 2. Clostridium perfringens (welchii), x2700. (Glaxo Laboratories, England) The unit of size in measuring bacteria is the micrometer, μτα (1 μϊΆ = T ÖVÖ mm). Escherichia coli, a typical rod, may be 3 μτΆ in length and 0-75 μπι in diameter, while Staphylococcus aureus, a coccoid form, may be 0-75—1 μτη in diameter. BACTERIAL ANATOMY The main features of the anatomy of the bacterial cell are shown diagrammatically in Fig. 3. The Cell Wall Structures immediately exterior to the cytoplasmic membrane may be defined as the cell wall.

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  Microbiology

  • Dave Wessner, Christine Dupont, Trevor Charles, Josh Neufeld(Authors)
  • 2020(Publication Date)
  • Wiley

    (Publisher)

  b. The rod- shaped bacterium Bacillus anthracis causes anthrax, whereas Escherichia coli typically is a non-disease-causing inhabitant of the intestines of many animal species. c. Vibrio cholerae are curved and cause cholera in humans. d. Spiral-shaped bacteria include spirochetes like Treponema pallidum, which causes syphilis in humans. SEM © David M. Phillips/Science Source FIGURE 2.2 Pleomorphic Mycoplasma These bacteria are very small (about one-tenth the size of E. coli cells). Lacking a cell wall, the cells may have an irregular shape—some may appear sphere-like, others more rod-shaped. Although cells may stick together, Mycoplasma are not multicellular. 38 CHAPTER 2 Bacteria and the cigar‐shaped Epulopiscium fishelsoni (Microbes in Focus 2.1) can be over 600 μm long. At the other extreme, some atypically small bacteria exist, too. Mycoplasmas, as we noted previously, are only 0.2 μm in diameter. In early 2015, researchers reported the identification of even smaller bacte- ria. These ultra‐small bacteria, which have not yet been culti- vated, appear to have a volume of approximately 0.009 μm 3 . These newly observed bacteria may be near the lower size limit for cellular life as we know it. After all, even a single ribosome, the machinery for protein synthesis, is roughly 50 nm (0.05 μm) in diameter, and even the smallest cell would have to contain multiple ribosomes, a genome, messenger RNA, and various key enzymes in the cytoplasm. As we have seen in this section, bacterial cells exhibit great variation in their shapes and sizes. All bacterial cells, however, also share many common properties. In the next section, we will begin to explore the various structures found within a typical bacterial cell, focusing on the functions of these structures and, in some cases, their evolutionary history. electron microscopes and light microscopes, allow us to see objects of different sizes (Figure 2.4).

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  Infrastructure and Activities of Cells

  Biotechnology by Open Learning

  • M.C.E. van Dam-Mieras, B C Currell, R C E Dam-Mieras(Authors)
  • 2016(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  Thus although each bacterial cell is small (perhaps weighing about 10* 12 g), on a weight to weight basis, bacteria have metabolic turnover rates 10,000 -1,000,000 times faster than, for example, large animals. These extremely fast rates of chemical turnover support 6 Chapter 1 bacilli spirillal cells vibrios very fast growth rates. Many prokaryotes can double their mass in 20-30 minutes. This, coupled with the diversity of metabolism displayed by these types of cells and the increasing ability to genetically modify them, makes these simple cells attractive for use in biotechnological processes. Shape Prokaryotic cells take up a limited number of general shapes (Figure 1.1). These are given special terms: • spherical cells are called cocci (singular = coccus = berry); • cylindrical rods are called bacilli (singular = bacillus = rod); • spiral shaped cells are called spirillal cells; • part spiral or comma shaped cells are called vibrios. Not all bacilli are exactly the same shape, some are long and thin (eg Clostridium sporogenesi, others short and fat {Bacillus megaterium), some have square ends, others are tapered (NB descriptive microbiology includes many words to describe these fine details such as fusiform, ellipsoid etc). We can perhaps imagine a continuous spectrum of cell shapes as shown in Figure 1.1. Figure 1.1 General shapes of prokaryotic cells. pleomorphism Some species of prokaryotes produce cells of more than one shape. Such cells are said to exhibit pleomorphism. Arrangement of prokaryotic cells The manner in which cells are arranged often reflect the way in which the cells grow and divide. Let us see if you can predict some of these arrangements. Consider a coccus which can grow and divide in one plane only. If we start with one cell and this grows and divides into two and then four, how will the cells be arranged? The architecture of prokaryotic cells 7 streptococci We now have a short chain.

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  eBook - ePub

  Bacteria and Viruses

  • Britannica Educational Publishing, Kara Rogers(Authors)
  • 2010(Publication Date)
  • Britannica Educational Publishing

    (Publisher)

  Vibrio cholerae , which causes cholera. Other shapes of bacteria include the spirilla, which are bent and rebent, and the spirochetes, which form a helix similar to a corkscrew, in which the cell body is wrapped around a central fibre called the axial filament.

  The bacterium Streptococcus mutans is an example of a spherical (coccus) bacterium. This species of bacteria commonly aggregates into pairs and short chains . David M. Phillips/Visuals Unlimited

  Bacteria are the smallest living creatures. An average-size bacterium, such as the rod-shaped Escherichia coli , a normal inhabitant of the intestinal tract of humans and animals, is about 2 micrometres (μm; millionths of a metre) long and 0.5 μm in diameter, and the spherical cells of Staphylococcus aureus are up to 1 μm in diameter. A few bacterial types are even smaller, such as Mycoplasma pneumoniae , which is one of the smallest bacteria, ranging from about 0.1 to 0.25 μm in diameter; the rod-shaped Bordetella pertussis , which is the causative agent of whooping cough, ranging from 0.2 to 0.5 μm in diameter and 0.5 to 1 μm in length; and the corkscrew-shaped Treponema pallidum , which is the causative agent of syphilis, averaging only 0.15 μm in diameter but 10 to 13 μm in length. Some bacteria are relatively large, such as Azotobacter , which has diameters of 2 to 5 μm or more; the cyanobacterium Synechococcus , which averages 6 μm by 12 μm; and Achromatium , which has a minimum width of 5 μm and a maximum length of 100 μm, depending on the species. Giant bacteria can be visible with the unaided eye, such as Titanospirillum namibiensis , which averages 750 μm in diameter, and the rod-shaped Epulopsicium fishelsoni

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  Biochemistry and Physiology of Bifidobacteria

  • Anatoly Bezkorovainy(Author)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  10 Although to date only small differences (e.g., in glycan chain length) have been found between cocci and rods, this does not invalidate the hypothesis that the macromolecular composition of the cell wall determines shape. Shape-determining characteristics are likely to reside in the degree and type of cross links, the length of the glycan chain, and the orientation of the peptidoglycan in relation to the cell surface.

  Other model systems designed to explain bacterial shape include (1) differential rate controls of cell wall synthesis, (2) the effects of surface tension, and (3) possible specific protein assembly systems in the cell wall.11

  The size of bifidobacteria (stationary phase of growth in “Difco Vit B12 Assay” and human milk 4 × 1 μm for B. bifidum var. pennsylvanicus), like other bacteria, is dependent on growth rate. Bacteria from the log phase of growth may be both larger and more variable in size than those in the experimental stationary phase.12

  II. LIGHT MICROSCOPIC MORPHOLOGY

  The genus Bifidobacterium has a pleomorphic cellular morphology that is dependent not only on the individual species, but on the media in which it is grown. B. bifidum is a Gram-positive, curved rod with a bifurcated end, giving a characteristic Y shape when present in the stool of the breast-fed infant.1 Depending on the composition of the culture media, B. bifidum can be maintained as either a curved rod, a curved bifid rod, or a highly branched bacterium.13 Very little morphologic evaluation has been performed in species other than B. bifidum. Scardovi14 and co-workers have grown all species of Bifidobacterium in TPY-agar slants and examined the bacteria with a phase-contrast microscope (see Table 1 ).* In this setting, many of the other species are also branched or bifid (see Figures 1 through 3 ). When bifidobacteria are grown in a “Difco Vit. B12 assay” media supplemented with human milk, they still exhibit highly pleomorphic forms (see Figures 4 through 6

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  eBook - ePub

  Handbook of Microbiology

  Condensed Edition

  • Allen I Laskin(Author)
  • 2019(Publication Date)
  • CRC Press

    (Publisher)

  Bergey's Manual of Determinative Bacteriology. Williams and Wilkins, Baltimore, Maryland (1957).

  3. Davis, B. D., Dulbecco, R., Eisen, H. N., Ginsberg, H. S., and Wood, W. B. ., Microbiology. Hoeber Medical Division, Harper and Row, New York (1968).

  4. Pr\xE9vot, A. R., Turpin, A., and Kaiser, P., Les Bacteries Anaerobies. Dunod, Paris, France (1967).

  5. Skerman, W. B. D., A Guide to the Identification of the Genera of Bacteria , 2nd ed. Williams and Wilkins, Baltimore, Maryland (1967).

  *  The author gratefully acknowledges the kind assistance of Dr. D. Kronish, Warner-Lambert Research Institute.

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  Aerobic Gram-Negative Rods

  Dr. Hubert A. Lechevalier

  Small Motile Rods Or Vibrios Causing Phage-Like Lysis Of Bacteria

  Bdellovibrio

  Vibrios or rods, 0.35 X 1-2 μ. They are motile with a single thick (28 nm) sheathed flagellum; speed of travel is estimated at 100 cell lengths per second. The organisms are capable of attachment to bacterial cells (usually Gram-negative) that they can penetrate. Multiplication takes place within the bacterial host cell (host-independent strains are known). Release of the extracellular form is effected by lysis of the host cell. Type species: B. bacterovorus, found in soil, water, and sewage (Starr, M. P., and Seidler, R. i.,Annu. Rev. Microbiol., 25, 649-678, 1971).

  Curved Rods Forming Half-Circles, Circles And/Or Coils

  Microcyclus

  Slightly curved rods about 1 μm long, forming horseshoe-like structures, closed ring-like cells, or even curved corkscrew-shaped filaments. They are non-motile and are found in fresh-water bodies and soil. The type species,M. aquaticus, is colorless; the growth of another species, M. flavus, is yellow (Raj, H. D., ,Int. J. Syst. Bacteriol, 20, 61-81, 1970).

  Rods Capable Of Fixing Atmospheric Nitrogen In Laboratory Media

  There are numerous reports of microorganisms that are capable of fixing atmospheric nitrogen non-symbiotically. Blue-green algae, fungi, and some bacteria, such as species of Azotobacter, Azotomonas and Klebsiella (Mahl, M. C., Wilson, P. W., Fife, M. A., and Ewing, W. H., J. Bacteriol, 89, 1482—1487, 1965), have been implicated. The most studied and probably the most important bacterial non-symbiotic nitrogen fixers belong to the genus Azotobacter.

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