Biological Sciences
Spiral Shaped Bacteria
Spiral-shaped bacteria, also known as spirilla, are a type of bacteria characterized by their helical or corkscrew shape. They are classified as Gram-negative bacteria and can be found in various environments, including water and soil. Some spiral-shaped bacteria are pathogenic and can cause diseases in humans and animals, while others are beneficial and play a role in processes such as nitrogen fixation.
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7 Key excerpts on "Spiral Shaped Bacteria"
- Khuntia, B K(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
( 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’. This ebook is exclusively for this university only. Cannot be resold/distributed. 5. Box-shaped or Square-shaped Bacteria (Arcula) They are flat, box-shaped bacteria with perfectly straight edges and sharp 90° angles at the corners. Smaller cells are usually perfectly squares (2×2µ), while larger cells are rectangular; about twice as long as they are wide (4×2µ). Each bacterium is a thin flexible sheet with smooth surface. After cell divisions, the cells remain attached to each other, producing large sheets of squares. It was first discovered in 1980 in natural salt ponds. 6. Appendaged Bacteria They possess extension of their cells, as long tubes in the form of stalk or hypha, or as buds. 7. Pleomorphic Bacteria These bacteria do not have any characteristic shape unlike all others described above. They can change their shape. In pure cultures, they can be observed to have different shapes. D. Structure of Bacteria The different parts of a generalised bacteria cell have been shown in Figure 2.3 and have been described as follows. This ebook is exclusively for this university only. Cannot be resold/distributed. Figure 2.3: Structure of a generalised bacteria cell 1. Flagella Bacterial flagella are thin filamentous hair-like helical appendages that protrude through the cell wall and are responsible for the motility of bacteria. Most of the motile bacteria possess flagella. Its length is about 10-15µ. Bacterial flagella are totally different from eukaryotic flagella in structure and mechanism of action. They are much thinner than the flagella or cilia of eukaryotic cells.
eBook - PDF- Dave Wessner, Christine Dupont, Trevor Charles, Josh Neufeld(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
In contrast, Staphylococcus cells tend to form clusters rather than chains (see Figure 2.1). Some bacteria do not exhibit regular shapes but may exhibit highly variable cell morphologies. These bacteria are referred to as pleomorphic. Examples of pleomorphic bacteria include members of the genus Mycoplasma, which do not make a cell wall and, as a result, do not have a regular shape (Figure 2.2). Connections As we will discuss in Section 7.4, most bacteria can be removed from solutions by passing the solutions through fine filters. Because of their small size and lack of a cell wall, mycoplasma cells often are not retained by these fine filters. Some bacteria grow in more complex multicellular arrangements (Figure 2.3). Soil bacteria of the Actinomycete group grow as irregularly branching filaments called hyphae that are composed of chains of cells. Hyphae can form three‐ dimensional networks called mycelia that can rise above the substrate, penetrate down into soil, or both. A distinc- tive multicellular arrangement found in cyanobacteria is the SEM SEM SEM LM SEM Staphylococcus aureus Streptococcus pyogenes Escherichia coli Vibrio cholerae Treponema pallidum Centers for Disease Control and Prevention/ Science Source © Eye of Science/Science Source NIAID/Science Source © Ami Images/Science Source © James Cavallini/Science Source d. Spirilla are spiral-shaped. c. Vibrios are slightly curved rods. b. Bacilli are rod-shaped. a. Cocci are spherical © Dr. Gary Gaugler/Science Source SEM Bacillus anthracis FIGURE 2.1 Common shapes of bacteria a. Sometimes found on skin, Staphylococcus aureus cells are spherical, as are Streptococcus pyogenes, which may cause mild or serious infections, including scarlet fever. 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.
eBook - PDF- I.C. Gunsalus(Author)
- 1960(Publication Date)
- Academic Press(Publisher)
The cell bodies of these organisms have various shapes (cf. salmonellae, cocci, and penicillin-treated specimens). The flagella have a pronounced helical shape and look as though they rotate around their axis like a turning corkscrew (at least when mov-ing slowly). This appearance is characteristic for a filament down which series of helical waves are propagated. On the reasonable assumption that the base of the flagellar bundle is unable to rotate relative to the bacterial body, a wave motion of this kind will tend to cause the bacterium to rotate in a direction opposite to that of the helical waves. The viscous resistance of the medium to such rotation will, however, only permit a slow rotation of the cell. In this way a torque is applied to the flagellar helix, making propulsion possible. The picture is somewhat different in the case of terminally flagellated bacteria, notably the spirilla. Here the helical shape of the flagella is often not very pronounced. The organelles create cones of revolution at the poles of the organisms and probably perform their role as motor organs mainly by making the body rotate. The pronounced helical shape of the cell body then makes the organism move through the medium. Pijper explains the motility of spirilla in terms of stretching and shorten-ing of the coils of the cell bodies with intermittent freewheeling. 91 How-ever, the present author is unable to see how an alternating stretching and shortening of a helix could make the body move steadily and thus cover any appreciable distance. Moreover, as in the case of bacterial semisomer-saults, which have been described earlier in this chapter, any motion of the spirilla due to freewheeling can go on only for extremely short periods of time after propulsion has ceased. In bacteria equipped with many flagella these organelles beat to a large extent synchronously, several flagella waving closely side by side in each flagellar bundle.
eBook - ePub- Jennifer Stearns, Michael Surette, Jennifer Stearns, Michael Surette(Authors)
- 2019(Publication Date)
- For Dummies(Publisher)
In this chapter, we give a bird’s-eye view of the structure of microbial cells. Then we go into some of the most important structures in detail. We discuss major differences between microbes — for instance, what differs between eukaryotic and prokaryotic microorganisms, as well as things that all cells have in common.Seeing the Shapes of Cells
We know that prokaryotic cells come in many different shapes and sizes because we can look at them under a microscope. A description of the shape of a cell is called the cell morphology. The most common cell morphologies are cocci (spherical) and bacilli (rods). Coccibacillus are a mix of both, while vibrio are shaped like a comma, spirilla are shaped like a helix (a spiral, sort of like a stretched-out Slinky), and spirochetes are twisted like a screw. Figure 4-1 shows these common cell morphologies.Although prokaryotes are unicellular organisms, their cells can be arranged in a few different ways, like chains or clusters, depending on how the cells divide:FIGURE 4-1: Cell morphologies.- Cocci bacteria that divide along a single plane form small chains of two cells called diplococci or long chains of multiple cells called streptococci.
- Cocci bacteria can also divide along multiple planes to form tetrads (two planes), cubelike sarcinae (three planes), or grapelike clusters called staphylococci (multiple planes).
- Similarly to the cocci, rod-shaped bacteria can divide to form double-celled diplobacilli or longer chains called streptobacilli.
eBook - PDF- H. S. Jennings(Author)
- 2019(Publication Date)
- Columbia University Press(Publisher)
Often they gather about small green plants (Fig. 25), and in some cases a large number of bacteria gather to form a well-defined group without evident external cause. How are such results brought about ? T o answer this question, we will examine carefully the behavior of the large and favorable form, Spirillum 1 (Fig. 23, c ) . Spirillum is a spiral rod, bearing a bunch of flagella at one end. In a thriving culture a large proportion of the indi-viduals bear flagella at both ends and can swim indifferently in either direction. It is said by good authorities that such specimens are pre-paring to divide. When Spirillum comes against an obstacle, it responds by the sim-plest possible reaction, — by a reversal of the direction of movement. In specimens with flagella at each end the new direction is continued till a new stimulation causes a new reversal. In bacteria with flagella at only one end, the movement backward is continued only a short time, then the forward movement is resumed. Usually when the forward movement is renewed, the path followed is not the same as the original path, but forms an angle with it; the bacterium has thus turned to one side. Whether this turning is due to currents in the water or other 1 There are several species of Spirillum found in decaying organic matter. The species have not been clearly determined in most of the work on behavior, and this is not of great importance, as the behavior is essentially the same in character throughout. 28 BEHAVIOR OF THE LOWER ORGANISMS accidental conditions, or, as is more probable, is determined in some way by the structure of the organisms, has not been discovered. In the infusoria, as we shall see, the latter is the case. The reversal of movement of course carries the organism away from the agent causing it. We find that the same reaction is produced when the bacterium comes to a region where some repellent chemical is diffus-ing in the water.
eBook - ePub- 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 UnlimitedBacteria 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
eBook - PDF- Karl Maramorosch(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
The human pathogen M. pneumoniae and a few animal mycoplasmas show a peculiar gliding motility (Bredt, 1979). The spiroplasmas, on the other hand, are distinguished by the helical or spiral morphology after which they have been named, and by different types of motility (see below). Examination of the morphology of the spiroplasmas may be performed by darkfield or phase-contrast microscopy and by electron microscopy of sap expressed from infected plants, sections of the phloem tissue, or of cultured cells (Fig. 3). The very detailed description presented by Cole et al. (1973) of the morphology and ultrastructure of S. citri may be re-garded as representative for all spiroplasmas. Examination by darkfield microscopy of broth cultures in the logarithmic phase of growth revealed a number of short, helical filaments and some small round cells. The length of the filaments usually varied from 2 to 4 urn. On prolonged incubation of postlog cultures, the filaments increased in length and at the same time showed a progressive loss of helicity together with a tendency to develop blebs. At a very late stage, increas-ing fragmentation and distortion of the filaments were observed and many round or irregular bodies appeared. Two types of motility were exhibited by the helical cells: a rapid rotatory or corkscrew motion which could reverse, thereby leading to a minimal back-and-forth progress, and a slow undulation and bending of filaments that did not lead to a change of their position. Loss of helicity on increasing age of the cultures was associated with loss of motility. Recently, a third type of spiroplasmal motility, translational locomotion, was de-monstrated in viscous liquid medium and on glass surfaces (Davis, 1978; Daniels et al., 1980). Motilitv is energy-de-pendent and is optimal at pH 7, as shown in the study of Daniels et al. (1980), who also found that spiroplasmas dis-play positive as well as negative chemotaxis.
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