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Table of Contents
- Becteria
- Introduction
- History of Bacteriology
- Origin and Evolution
- Classification and Identification
- Morphology
- Cellular structure
- Gram positive and gram negative bacteria
- Metabolism of Bacteria
- Nitrogen Fixation
- Locomotion
- Endospore
- Bacterial Reproduction.......................................................................................................................................................................................................................................
- Bacterial Cell Growth and Division
- Bacteria as pathogens
- Bacteria in Technology and Industry
- Wall less forms of Bacteria
- Summary
- Exercises
- Glossary..............................................................................................................................................................................................................................................................
- References
- Bacteria
- Contents......................................................................................................................................................................................................................................................
- Etymology
- Origin and early evolution
- Morphology
- Cellular structure
- Intracellular structures
- Extracellular structures
- Endospores
- Metabolism
- Growth and reproduction
- Genetics
- DNA transfer
- Bacteriophages
- Behavior
- Secretion
- Bioluminescence
- Multicellularity
- Movement
- Classification and identification
- Interactions with other organisms
- Predators
- Mutualists
- Pathogens
- Significance in technology and industry
- History of bacteriology
- The bacterial cell
- Bacteria as prokaryotes
- Diversity of structure of bacteria
- Morphological features of bacteria
- The Gram stain
- The cell envelope
- Capsules and slime layers
- Flagella, fimbriae, and pili
- The cytoplasm
- Genetic content...........................................................................................................................................................................................................................................
- Cytoplasmic structures
- Biotypes of bacteria
- Bacterial cell structure....................................................................................................................................................................................................................................
- Contents......................................................................................................................................................................................................................................................
- Cell morphology[edit]
- Cell wall[edit].............................................................................................................................................................................................................................................
- The gram-positive cell wall[edit]
- The gram-negative cell wall[edit]
- Plasma membrane[edit]
- Extracellular (external) structures[edit]
- Fimbriae and pili[edit]............................................................................................................................................................................................................................
- S-layers[edit]
- Glycocalyx[edit]
- Flagella[edit]
- Intracellular (internal) structures[edit]
- The bacterial DNA and plasmids[edit]
- Ribosomes and other multiprotein complexes[edit]
- Intracellular membranes[edit]
- Cytoskeleton[edit]
- Nutrient storage structures[edit]
- Endospores[edit]
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Course: Paper I: DC-I: Phycology and Microbiology
Book: Bacteria
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Date: Friday, 16 September 2016, 05:16 PM
Table of Contents
Becteria
Introduction
History of Bacteriology
Origin and Evolution
Classification and Identification
Morphology
Cellular structure
Gram positive and gram negative bacteria
Metabolism of Bacteria
Nitrogen Fixation
Locomotion
Endospore
Bacterial Reproduction
Phycology and Microbiology
Unit-I
Lesson: Bacteria
Lesson Developer: Vibha Narang
College/Department: ARSD College, University of Delhi
Introduction
Video: Diversity of bacteria
Source: http://www.britannica.com/EBchecked/topic/48203/bacteria/39337/The-cell-envelope?anchor=ref
Bacteria (singular: bacterium) are unicellular microorganisms. They are microscopic organisms that form large colonies and multiply very fast. They cause diseases but are still very essential for the ecosystem. Bacteria help getting rid of dead organisms as they play the role of decomposers in the food web. They are single celled organisms, devoid of a membrane-enclosed nucleus. They breakdown organic material (decaying plant and animal tissues) into their mineral components and supply plant with nutrients for growth.
Bacteria are present on a variety of habitat on earth. They are found in soil, atmosphere, acidic hot springs, soil contaminated with radioactive waste, seawater, and deep in the oceans.Bacteria exhibit wide range of shapes. They may vary from rod like bacilli to spherical cocci to spirals.
The study of bacteria is called Bacteriology. Bacteria can be identified by their morphology, temperature and growth requirement.
History of Bacteriology
Antonie van Leeuwenhoek first observed bacteria in 1676 by using a single lens microscope, which he designed himself. He named these bacteria ‘animalcules’.
Christian Gottfried Ehrenberg in 1828 gave the name ‘bacterium’. It was the French Chemist Louis Pasteur and the German physician Robert Koch who studied the role of specific microorganisms in causing specific fermentations and diseases. This resulted in the study of bacteriology.
Pasteur created an experimental system for cultivating microbes in artificial media. Theodor Schwann designed an apparatus for observing alcoholic fermentation in the presence of air. His experiments involved the use of microscopic life.
Table: A brief history of bacteriology.
Source: Author
1676 Anton van Leeuwenhoek first discovered bacteria with a single lens microscope
Ferdinand Cohn identified some of the first photosynthetic bacteria and proposed taxonomy for this microorganism. 1828 Christian Gottfried Ehrenberg introduced the name bacterium. 1853 Ferdinand Cohn categorized bacteria in four gropus based on their shapes- sphericals, short rods, long rods- threads and spirals 1857 Louis Pasteur demonstrated that the lactic acid fermentation is caused by the growth of microorganisms 1876 - 77 Robert Koch demonstrated that anthrax is caused by Bacillus anthracis 1877 Thomas J. Burrill first discovered bacteria as causative organisms of plant diseases 1884 Danish Physician, Hans Christian Gram developed a widely used microbiological staining technique (Gram staining) that is still used in the identification and characterization of bacteria. 1887 S. Winogradsky, a Russian microbiologist pioneered concept of biogeochemical cycle. He reported that Beggiatoa oxidized hydrogen sulphide as an energy source and formed intracellular sulphur droplets. He discovered the first known form of lithotrophy. 1890 Robert Koch founder of modern bacteriology published the postulates which are four criteria designed to establish a relationship between a causative microbe and a disease. 1910 Paul Ehrlich developed the first drug for syphilis 1915 - 1917 Felix de Herelle, a French Canadian Microbiologist, discovered bacteriophages with other colleagues 1928 British bacteriologist Frederick Griffith observed that nonvirulent pneumococcal bacteria became virulent when injected into mice along with dead virulent Pneumococcus thus initiating the understanding of gene transfer among bacteria. 1947 Lederberg and Tatum showed that the bacterium Escherichia coli entered a sexual phase during which it could share genetic information through bacterial conjugation. 1977 Carl Woese observed that archaea have a separate line of evolutionary descent from bacteria and eukaryotic life forms.
Origin and Evolution
Stromatolites are oldest fossils of bacteria about 3.5 billion years old. They are rock like structures and have many layers of bacteria and sediments. Biogenic processes led to their formation.
Figure: Stromatolites
Source:http://en.wikipedia.org/wiki/File:Stromatolithe_Pal%C3%A9oarch%C3%A9en_-MNHT.PAL.2009.10.1.jpg
Single celled microorganisms were ancestors of modern bacteria. They were the first forms of life to develop on earth, about 4 billion years ago. During those times oxygen was scarce, but factors such as temperature and atmospheric radiation were more common. All organisms were microscopic, and bacteria and archaea were the dominant forms of life. A hyperthermophile that lived about 2.5 billion–3.2 billion years ago is considered to be the ancestor of these two dominant forms of life.
Figure: Opalescent Pool in Yellow Stone National Park, Wyoming USA. These hot springs have conditions similar to those that were found on primitive earth. The bright colors of these hot springs are due to the presence of archaebacteria. Source:http://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Opal_Pool_YNP2_filtered_noise.jpg/284px-Opal_Pool_YNP2_filtered_noise.jpg
Classification and Identification
Classification describes the diversity of bacterial species. It names and groups organisms based on their similarities. Bacteria are classified on the basis of cell structure, cellular metabolism and the differences in cell components.
The science of molecular systematics is a new field, which allows systematists to test evolutionary relationships at basic level. This in case of prokaryotes showed that they consist of two separate domains – Eubacteria and Archaebacteria. Presently they are called Bacteria and Archaea. The Archaea and Eukaryotes are closely related to each other than either is to bacteria. Eukarya, Archaea and Bacteria are the basis of the three domain system of classification. This is the most widely accepted classification system in biology.
The Eukaryotic cells have a well defined nucleus which is membrane-enclosed, many membranous organelles like mitochondria, Golgi bodies, ER, lysosomes, chloroplasts etc., whereas, the Archaea and Bacteria are unicellular organisms which do not develop into multicellular forms. The cells are adjacent to one another and remain enclosed in a common sheath or slime secreted by the cells.
Linkage
Ester linkages.
It is more permeable to ions etc.
Ether linkages.
It is less permeability
Ester linkages
Flagellar structure Consisting of 3 parts- filament, hook and basal body
Like bacterial Type IV pili 9 + 2 organisation
Membrane bound nucleus and nucleolus
Absent. Absent. Present.
Genome –
DNA covalently closed & circular
Introns and Histones
Present
Absent
Present
Present in some
Absent
Present
tRNA-
Thymine in TψC arm
Initiator amino acid
Present
Formylmethionine
Absent
Methionine
Present
Methionine
Transcription-
mRNA splicing, capping, poly A tail addition
RNA polymerase number and subunits
Absent
One, 4 subunits
Absent
One, 8-12 subunits
Present
Sensitivity to Rifampicin
Polycistronic mRNA
RNA polymerase typeII promoter
Presence of Operons
Sensitive
Present
Absent
Present
Insensitive
Present
Present
Present
Three, 12- 14 subunits
Insensitive
Absent
Present
Absent
Membrane bound organelles Absent Absent Present
Ribosomes Size 70S 70S 80S
Endospores
Gas vesicles
Poly-β-hydroxyalkanoates storage granules
Present
Present
Present
Absent
Present
Present
Absent
Absent
Absent
Growth
Above 70o^ C
Above 100o^ C
Present
Absent
Present
Present
Absent
Absent
Sensitivity to antibiotics
Morphology
Bacteria are a diverse group of organisms. They vary in size, shape, habitat and metabolism. The length of a bacterial cell varies from 0.5 to 5.0 μm. Mycoplasmas are the smallest bacteria and measure 0.3 μm. The largest bacterium is Thiomargarita namibiensis. It is a spherical bacteria 0.75 mm in diameter and is visible with the naked eye. This bacterium shines like a pearl. It eats sulfur and is found in chains of 10 or more. They can reduce nitrate and oxidize sulfide into sulfur, which is stored in their cytoplasm as sulfur granules. Morphologically bacteria exhibit three shapes.
Bacteria can have any of the following three shapes
● Spheroidal (cocci)
● Cylinderical (bacilli or rods) and
● Spirillar (spirochetes).
Figure: Bacterial Morphology
Source: http://en.wikipedia.org/wiki/Bacterial_cellular_morphologies
Figure: Arrangement of cocci bacteria
Source: http://en.wikipedia.org/wiki/File:Arrangement_of_cocci_bacteria.svg
Bacilli
Bacilli are rod shaped bacteria. These often occur in chains. They may occur solitary or in combination to form diplococci or streptobacilli. Bacillus anthracis is a bacillus bacterium, which causes anthrax.
A B
Figure: Rod shaped bacilli E.Coli – A Light microscope image of gram stained bacteria and B. Electron micrograph of the same.
Source:http://en.wikipedia.org/wiki/Bacillus,http://en.wikipedia.org/wiki/File:EscherichiaColi_NIAID.jpg
Spirillum
These bacteria have a cell body that twists like a spiral. They are solitary bacteria and may rarely occur in chains. They are of two types – one is short rods which are slightly bent (“comma” shaped or Vibrio) and long rods with many bends.
Spirillum is a gram negative bacteria. It is spirally twisted and has tufts of flagella at both poles. It is found in stagnant water and is a causal organism of various human diseases.
Figure : Spirillum
Source: http://en.wikipedia.org/wiki/File:Spirillen.jpg
Spirochete
Spirochetes are spiral bacteria with rigid rods which are highly motile through an axial filaments/endoflagella that is present in the periplasmic space.
