Bacillus spp

5 Key excerpts on "Bacillus spp"

• 

  eBook - ePub

  Foodborne Diseases

  • Alexandru Mihai Grumezescu, Alina Maria Holban(Authors)
  • 2018(Publication Date)
  • Academic Press

    (Publisher)

  Bacillus spp. relevant to the dairy industry, virulence potential, and biofilm production from the perspective of food safety.

  Keywords

  Bacillus spp. virulence enterotoxins biofilms

  1. Bacillus : General Information

  Bacillus spp. bacteria show a wide range of characteristics that allow them to live in most natural environments (Griffiths, 2010 ). Bacillus comprises a large group of ubiquitous Gram-positive, rod-shaped, aerobic-to-facultatively anaerobic, endospore-forming saprophytes (Weber and Rutala, 1988 ). Although the majority of Bacillus spp. are nonpathogenic, a few (B. cereus, B. anthracis , and B. thuringiensis ) opportunistically infect animal hosts (mammals and insects) (Vilain et al., 2006 ). Bacillus microscopic morphology may be individual or as long chains in primary isolates from soil or water samples (Weber and Rutala, 1988 ). The size of an individual rod can range from 0.5 × 1.2 to 2.5 × 10 μm2 . Spores produced by Bacillus spp. are resistant to heat (including to some extent, pasteurization conditions), cold, ionizing radiation, dehydration, and many disinfectants (Griffiths, 2010 ). The endospores are either oval or cylinder shaped and are found centrally, subterminally, or terminally. Over 30 species of Bacillus spp. are recognized and are divided into two groups based mostly on the 16S rRNA/DNA sequences: the B. subtilis group and the B. cereus group. B. subtilis , B. amyloliquefaciens , B. licheniformis , and B. pumilus are mesophilic, have ellipse shaped spores, and are the most common members of the B. subtilis group. B. cereus , B. anthracis , B. thuringiensis , B. weihenstephanensis , and B. mycoides do not ferment mannitol, produce lecithinase, and comprise the B. cereus group.

  The colony morphology of Bacillus spp. is diverse across species. Bacillus spp. grow on nutrient agar or peptone media and exhibit ideal growth at a pH of 7; however, some Bacillus spp. grow at a pH of 9, while other species can endure pH 2. Bacillus spp. grow best within a temperature range of 30°–45°C, but thermophilic variants grow optimally at 65°C. All Bacillus spp. metabolize organic substrates, such as amino acids, organic acids, and sugars, by aerobic respiration, anaerobic respiration, or fermentation, depending on species and environment. The enzymatic processes and metabolic characteristics are the typical criteria for Bacillus

  Sign up to read

  Learn more about book
• 

  No longer available |Learn more

  Microbiology for Surgical Technologists

  • Margaret Rodriguez(Author)
  • 2016(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  The challenge for steam sterilizers is to kill the measured population of Geobacillus stearothermophilus in a test ampule or strip. When the sterilized BI has been incubated and shown to have no growth, the sterilizer is considered to be working properly and the instruments processed by this method are considered sterile. Overview of Bacilli Chapter 4 discussed the various ways species of bacteria are classified based on their shape, oxygen requirements, stain- ing results, and motility. Bacilli are rod-shaped bacteria that are Gram-positive on staining; however, some species will become Gram-negative in their mature form and therefore may be listed in the literature as Gram-variable. Most species are catalase-positive. Bacilli are found in soil samples around the world and also in animal intestinal tracts. They are saprophytes, which Figure 13-1 Bacillus cereus subsp. mycoides: Gram stain. Note the rod-shape of the bacilli. Courtesy of CDC/Dr. William A. Clark Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. CHAPTER 13 Gram-Positive Bacilli 187 Bacillus anthracis Bacillus anthracis has been causing disease in humans for centuries. It was the first species of bacteria proven to be directly responsible for causing disease in humans. As discussed in Chapter 1, Robert Koch grew the bacteria in laboratory culture in 1877, showing its ability to form spores, and injected the cells into animals to produce the anthrax disease (see Figure 13-2). The bacteria are viewed as single or paired in clinical specimens and as long chains in laboratory cultures.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Sustainable Aquaculture Techniques

  • Martha Patricia Hernandez- Vergara, Carlos Ivan Perez-Rostro, Martha Patricia Hernandez- Vergara, Carlos Ivan Perez-Rostro(Authors)
  • 2014(Publication Date)
  • IntechOpen

    (Publisher)

  should be applied. Bacillus spp. are isolated almost ubiquitously from soil, water, mud, sediment, dust, air and the surfaces and organs of aquatic animals [23]. They have been isolated from fish, crustaceans, bivalves and shrimps and have been found in the micro‐ flora of the gills, skin and intestinal tract [19,24]. One effective strategy being used in developing countries is the isolation of Bacillus spp. from commercial ponds and then using selected isolates as commercial products [24]. Bacilli are classified as endospore forming Gram-positive rods and cocci and isolation procedures must selectively enrich for these organisms while excluding other genera in the same group. In one study, methods used for isolating various Bacillus strains were based mainly on the resistance of their endo‐ spores to elevated temperatures [111]. The technique used involved blending of samples with an enrichment medium, which also induced vegetative cells to sporulate, followed by incubation to allow formation of mature spores in large quantities. The isolation involved heat treatment for the selection of spores from Bacillus species. Ethanol is also a useful disinfectant and dehydration agent to use for isolation of Bacillus strains as its application kills vegetative cells, whereas the more resistant endospores survive. The resistance of Bacilli to the antibiotic polymyxin B also enables use of this antibiotic for the selection of this group of bacteria whilst eliminating most Gram-negative bacteria. Once selected, cells can be characterised by their morphology, typically using microscopic techniques, by use of gram staining and by quantification of the activity of enzymes such as catalase [111]. 6.2. In vitro screening and selection of aquaculture biological agents To appropriately select biological agents it is essential to understand the mechanisms of action and to define selection criteria for potential probiotics [112].

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Structure

  • I.C. Gunsalus(Author)
  • 1960(Publication Date)
  • Academic Press

    (Publisher)

  The circumstances which induce bacteria to form spores and the chemi-cal changes which they undergo during this process have been discussed at several recent symposia. 3 ' 4 Of particular interest are the well-designed 207 208 C. F. ROBINOW F I G . 1. Spores in Bacillus cells. A: unidentified bacillus isolated from soil; B : B. cereus; C: B. megateriuvi 350. Note the serrated contours of the spores. Details of their sculptured surface are shown in Figs. 14-16. Ordinary microscopy. A and B fixed with osmium tetroxide, photographed unstained between agar and a coverslip. C fixed with alcohol, stained lightly with 0.25% thionin. studies of Grelet, 5 8 whose experiences have been put to good use in a com-bined chemical and cytological study of spore formation 9 which Dr. Eliza-beth Young has recently carried out in the laboratory of Dr. P. C. Fitz-James. MORPHOLOGY OF BACTERIAL SPORES 209 FIG. 2. Successive stages in the release of spores from dissolving vegetative forms of the bacillus from soil illustrated in Fig. 1 A. The density of the sporing rods decreases from left to right in this fortuitously but conveniently arranged sequence. Phase-contrast microscopy (X 3900). The chemistry and physiology of spores are discussed elsewhere in this work. The present chapter is concerned with their anatomy. II. Distribution of the Ability to Form Spores The best-known spore formers are the rod-shaped bacteria of the two genera Bacillus and Clostridium, but certain cocci 10 and spirilla 11 · 12 are also able to form spores. Shiny, oval bodies looking like large bacterial spores have repeatedly been seen extending through several cells of the trichomes of Oscillospira guilliermondi 12 · 13 (Fig. 3). This occasional inhabitant of the cecum of guinea pigs has features reminiscent of the genus Oscillatoria of the blue-green algae, but is now counted among the bacteria 14 because of its lack of pigments, its peritrichous flagellation and rapid, sinuous swim-ming movements.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Biotechnology In India

  Initiatives And Accomplishments

  • Niladri Bag(Author)
  • 2020(Publication Date)
  • NEW INDIA PUBLISHING AGENCY (NIPA)

    (Publisher)

  Recently, some workers reported nitrogen fixation in different species of Bacillus (Kumar et al . 2012). It is very likely that plant growth promotion by rhizosphere bacilli may be a result of combined action of two or more of these mechanisms. Pathogenic 92 Biotechnology in India microorganisms affecting plant health are a major threat to food production, and traditional methods, viz., crop rotation, breeding for resistant plant cultivars, and application of chemical pesticides, seem to be insufficient to control root diseases of important crop plants (Johri et al . 2003). Biological control of pathogens has been increased in the past few years partly due to change in the public concern over the use of chemicals and the need to find alternative of chemicals for disease control. Bacillus species express antagonistic activities by suppressing the pathogens (Chen et al . 2009a, b; Arrebola et al . 2010 and Kumar et al . 2012; Oslizlo et al . 2015). Enhancement of plant growth by root-colonizing species of Bacillus is well documented. Spore-forming bacilli have an advantage over the non-spore formers such as Pseudomonas . Spores are more robust and resistant to the elevated temperature and high concentrations of chemicals. Moreover, the shelf-life of biological products based on bacterial spores can be up to 1-3 years. A disadvantage of using the spores is the requirement of time to return to the metabolic active stage of a vegetative cell after their application. In the past few years, research has been directed more toward the induced systemic resistance (ISR). Induced resistance may be defined as a physiological state of enhanced defensive capacity elicited in response to specific environmental stimuli and consequently the plants innate defenses are potentiated against subsequent biotic challenges (van Loon 2000). Choudhary and Johri (2008) have reviewed ISR by Bacillus spp.

  Sign up to read

  Learn more about book