Biological Sciences
Spirochaete Bacteria
Spirochaete bacteria are a group of spiral-shaped, motile bacteria that are characterized by their unique flagella and flexible cell walls. They are found in diverse environments, including soil, water, and the gastrointestinal tracts of animals. Some spirochaetes are pathogenic and can cause diseases such as syphilis, Lyme disease, and leptospirosis.
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eBook - ePubHandbook of Microbiology
Condensed Edition
- Allen I Laskin(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
The Spirochaetales Dr. Robert M. SmibertMembers of the order Spirochaetales are slender, flexuous, unicellular, helically coiled organisms 5 to 500 μm long and 0.1 to 3 μm wide; they have one or more complete turns in the helix. The organisms are Gram-negative, but are best observed by dark-field microscopy or phase-contrast microscopy. They are motile, with a rapid whirling about the long axis of the cell, flection, and movement in a corkscrew or serpentine fashion. Spirochetes consist of an outer cell envelope and an inner protoplasmic cylinder. Between the cell envelope and the protoplasmic cylinder are axial fibrils that are inserted into the cylinder wall at each end of the cell and extend along the cell towards the opposite end of the cell. Bizarre forms of spirochetes may be seen. Bullae, for example, are swellings of the cell envelope. In old cultures, spirochetes may coil up, forming spheres or coccoid forms that may break up into granules. The coccoid forms and granules are also found in cultures treated with chemicals such as penicillin.1 Spirochetes are both aerobic and anaerobic. They are found free-living or saprophitic in nature or are parasitic. Some species are pathogenic for man and animals.The genera of Spirochaetales may be divided into two groups on the basis of their relationship to oxygen. Anaerobic genera include Spirochaeta, Borrelia, Treponema , and Cristispira ; the obligate aerobic genus is Leptospira.Spirochaeta are found free-living in nature. Some are anaerobes, others are facultative anaerobes. They are not very strict anaerobes.Borrelia cause relapsing fever in man and are transmitted by lice and ticks. They are not very strict anaerobes.Treponema are found in the intestines, oral cavity, and genital tract of man and animals. Some are pathogens. They are anaerobes and range from strict anaerobes to those that will tolerate some oxygen.Cristispira
eBook - PDF- N. A. Logan(Author)
- 2009(Publication Date)
- Wiley-Blackwell(Publisher)
In 16S rRNA sequence comparisons strains of L. biflexa and L. interrogans show a closer evolutionary rela- tionship to each other than they do to Leptonema illini, and the three rep- resent a branch quite distinct from the other spirochaetes (Fig. 7.2). Important species Chapter 7 The spirochaetes Spirochaetes are major parasites and pathogens of humans and other ani- mals. Epidemiologies are diverse, but in many cases the organisms gain entry through skin or mucous membranes, then appear in the blood and become widely disseminated, causing multistage diseases which may have periods of latent infection, and show tropisms for the skin, heart and central nervous system. Humans are the natural hosts of Treponema pallidul11 subsp. pallidul11, the cause of venereal and congenital syphilis, T. pallidul11 subsp. endemicul11, the cause of endemic syphilis, T. pallidum subsp. pertenue 103 8 Helical and curved bacteria The elegance of form of the organisms exerted a fascination not stimulated by the usual bacteria to which one is so accustomed. M.A. Williams & S.c. Rittenberg, 1957, A Taxonomic Study of the Genus Spirillum Ehrenberg Introduction This group contains 10 genera whose members have similar cellular mor- phologies and share some other characteristics. Compared with the spirochaetes, however, it is not well defined phenotypically or phyloge- netically and some parts are best regarded as loose assemblages which require comprehensive genotypic study before satisfactory arrangements can be made. Members of the group typically have inflexible, Gram-negative, heli- cally curved cells whose numbers of turns range from less than one to many. Emphasis on this morphological character has been tempered by the occurrence of straight rod variants in some species and the existence of organisms which share several characters with Aquaspirillum species but normally occur as straight rods.
- 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.
- Jason Birkett, John Lester(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
These are aerobic, Gram-negative bacteria characterized by an outer slime layer and the ability to move by gliding. Found in soil and water, many are capable of degrading and assimilating other micro-organisms and some can digest cellulose. One of the two orders is characterized by production of fruiting bodies.2.4.3 Sheathed bacteria
The sheathed bacteria are rod-shaped organisms which grow in chains surrounded by a gelatinous sheath. The sheaths may attach to solid surfaces by holdfasts or accumulate surface encrustations of iron and manganese oxides. Examples are Leptothrix, Sphaerotilus and Streptothrix, which occur in both clean and polluted water. Streptothrix and particularly Sphaerotilus filaments are common in activated sludge and are thought to be responsible for sludge bulking and poor settling.2.4.4 Budding and/or appendaged bacteria
Bacteria which are morphologically identified by appendages such as stalks (e.g. Caulobacter) or hyphae (e.g. Hyphomicrobium) are included in this group. They are widely distributed in soil and water containing iron (II) salts and are thus occasionally problematic at water treatment works.2.4.5 Spirochaetes
These are Gram-negative chemotrophs characterized by their flexible helically coiled shape. The group includes free-living, parasitic and pathogenic aerobes and facultative anaerobes. The largest in size, Spirochaeta, are freeliving aquatic organisms found in fresh or polluted water, sewage or mud, often in anaerobic conditions. The smaller Treponema and Leptospira include pathogenic species causing syphilis (T.pallidum) and leptospirosis or Weil’s disease (L.icterohaemorrhagiae), the latter being of particular concern to those working with sewage.2.4.6 Spiral and curved bacteria
Distinguished by their rigidity and the possession of flagella rather than axial filaments, this group contains two Gram-negative genera, Spirillum and Campylobacter. These are either free-living aquatic aerobic or microaerophilic, e.g. Sp. anulus, or anaerobic or microaerophilic parasitic or pathogenic organisms, e.g. Sp. minor. Campylobacter foetus causes abortion in sheep and cattle. Related genera include Bdellovibrio
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