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Rod-shaped bacteria are the type of bacteria that comes under the genus Bacillus. These are soil microorganisms that are capable of withstanding extreme conditions such as high pH, temperature, and high salt levels. These rod-shaped bacteria are divided into gram-positive and negative bacteria. The ribosomes are scattered throughout the cytoplasm, which helps in protein synthesis.
- These bacteria possess flagella that help transfer genetic characters through a process called conjugation.
- Some important qualities of rod-shaped bacteria include the ability of organisms to produce with the help of spores and help in nitrogen fixation.
- They provide valuable insights into the vast world of microbes and help in the field of food production and biotechnology.
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What is Rod-Shaped Bacteria?
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Rod-shaped bacteria are microscopic organisms that appear elongated and cylindrical in shape. Some of these species are pathogenic and help in the process of digestion. Some common examples of rod-shaped bacteria include Salmonella typhi, Streptobacillus and Brucella.
- The two components that make up the rod-shaped cell are caps at either end and a cylinder in the middle portion.
- In these bacteria, the cell membrane is positioned beneath the cell wall, which acts as an important site for producing energy.
- The cell wall helps regulate osmotic pressure and cellular traffic and contributes to pathogenicity.
- Lactobacillus is a type of rod-shaped bacteria that is used in the production of yogurt and other fermented foods.
- The morphology of a bacterial cell determines both its shape, and the capacity to cause diseases.
- The rod-shaped bacteria have a greater surface area-to-volume ratio, which increases the efficiency of their intake of nutrients.
Also Read: Prokaryotic Cells
Types of Rod-Shaped Bacteria
Types of Rod-Shaped Bacteria
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Rod-shaped bacteria can be categorized according to a number of factors, including oxygen requirements, biological roles, and Gram staining. They vary in both morphology and function. Based on the position, rod-shaped bacteria are categorized into various types:
- Streptobacilli
In these bacteria, organisms are grouped in the form of chains. Streptobacillus moniliformis is the most common example of Streptobacilli.
- Dipliobacilli
Dipliobacilli includes two rod-shaped bacteria that are present adjacent to each other. Enterobacter aerogenes is the most common example of Dipliobacilli.
- Coccobacilli
Coccobacilli are short bacilli with a width that is about equal to their length. The most common example of this category include Haemophilus influenzae.
- Palisades
Palisades are groups of cells aligned perpendicular to one another. Example- Corynebacterium diphtheriae.
Also Read: Staining: Types, Mechanism & Techniques
Examples of Gram Positive Rod-Shaped Bacteria
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Gram-positive bacteria consist of a thick layer of peptidoglycan in the bacteria cell wall, which gives positive results in gram stain tests. Some of the examples of gram-positive, rod-shaped bacteria are:
- Eubacterium
- Clostridium
- Mycobacteria
- Streptomyces
- Actinomyces
- Bifidobacterium
- Nocardia
Examples of Gram Negative Rod-Shaped Bacteria
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Gram-negative bacteria have a thin peptidoglycan layer that appears pink under the microscope. Examples of gram-negative rod-shaped bacteria include:
- Escherichia coli
- Salmonella
- Bacteroides
- Prevotella
- Proteus
- Staphylococcus
- Fusobacterium
Aerobic & Anaerobic Rod-Shaped Bacteria
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Based on consumption of oxygen, rod-shaped bacteria can be further classified into two categories:
Aerobic Rod-Shaped Bacteria
Aerobic bacteria is a type of bacteria that needs oxygen for survival. Some common examples of this category include:
Examples of aerobic gram-positive bacilli
Some common examples of aerobic gram-positive bacilli are as follows:
- Bacillus (facultative anaerobes)
- Corynebacterium
- Listeria (facultative anaerobes)
- Nocardia
Examples of aerobic gram-negative bacilli
Some common examples of aerobic gram-negative bacilli are as follows:
- Pseudomonas aeruginosa
- Enterobacter (facultative anaerobes)
Anaerobic Rod-Shaped Bacteria
Anaerobic bacteria are able to carry out oxygen-free metabolic processes, including fermentation. An important source of infections in both humans and animals is non-sporing anaerobes. Some common examples are:
Examples of anaerobic gram-positive bacilli
Some common examples of anaerobic gram-positive bacilli are as follows:
- Lactobacillus – L.acidophilus
- Bifidobacterium – B.dentium
- Eubacterium – E. brachy
- Propionibacterium – Cutibacterium acnes
Examples of anaerobic gram-negative bacilli
Some common examples of anaerobic gram-negative bacilli are as follows:
- Fusobacterium – F.nucleatum
- Bacteroides – B.fragilis
- Leptotrichia – L.buccalis
Diseases caused by Rod-Shaped Bacteria
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The common routes for diseases caused by rod-shaped bacteria in humans are through:
- Contaminated foods
- Polluted Water
- Contact with sick people or infected animals
Some of the important diseases caused by rod-shaped bacteria include:
| Diseases | Causal Organisms | Route |
|---|---|---|
| Anthrax | Bacillus anthracis | Through cuts, and contact with infected animals. |
| Typhoid | Salmonella typhi | Contaminated food, or water |
| Tetanus | Clostridium tetani | Cuts or wounds caused by sharp, and contaminated objects. |
| Diphtheria | Corynebacterium diphtheriae | Direct contact, and air. |
| Plague | Yersinia pestis | Air, Faecal route, Oral or through Vectors. |
Rod Bacteria Vs Coccus Bacteria
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The difference between rod bacteria and coccus bacteria are as follows:
| Rod Bacteria | Coccus Bacteria |
|---|---|
| Rod-shaped bacteria are also called bacilli. | Coccus bacteria are a type of bacteria that are round, oval, or spherical in shape. |
| Some examples of gram-positive bacilli include Mycobacterium, Clostridium and Nocardia. | Some examples of gram-positive cocci include Streptococcus, Staphylococcus and Enterococcus. |
| Gram-negative bacilli include Fusobacterium,Bacteroides and Leptotrichia. | Gram-negative cocci include Acidaminococcus and Anaeroglobus, Veillonella. |
Things to Remember
- Rod-shaped bacteria form a rod-like structure and help the bacteria survive in adverse conditions.
- Gram-positive and Gram-negative types of bacteria are distinguished using the 'Gram Stain' method.
- Bacillus anthracis is a gram-positive, rod-shaped bacteria that causes the deadly disease known as anthrax.
- Endospores are formed in these types of bacteria.
- The hair-like projections known as "pili" or "fimbriae" on a large number of Gram-negative bacteria help them adhere to host cells.
- Many of these bacteria are not harmful; however, some, including Bacillus cereus and Bacillus anthracis, can be harmful.
Sample Questions
Ques. What are the common examples of cocci and rod-shaped bacteria? (3 marks)
Ans. Most rod bacteria, or bacillus, have a cylindrical or rod-like structure. On the other hand, coccus has a spherical or round structure.
- Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli are a few examples of rod-shaped bacteria, or bacilli.
- Streptococcus pneumoniae and Staphylococcus aureus are two examples of cocci bacteria.
Ques. What are some defining characteristics of bacteria? (3 marks)
Ans. The following are the characteristics that define bacteria:
- Bacteria are unicellular prokaryotes.
- They could be rod-like, elliptical, spherical, comma-shaped, or even exist in clusters.
- They use binary fission to reproduce rapidly.
- Humans can benefit greatly from some bacteria, such as those used to make curd, but others can lead to diseases like cholera and typhoid.
Ques. Can bacteria survive without oxygen? (2 marks)
Ans. Yes, bacteria can grow and thrive in environments without oxygen. Such bacteria are called anaerobic bacteria. They are the source of a few diseases like gangrene and tetanus.
Ques. In what way do bacteria obtain their nutrition? (2 marks)
Ans. In order to carry out their biochemical activities, they need water, metals, hydrogen, oxygen, and nitrogen. Bacteria get energy from two basic sources. Bacteria that are capable of producing their own food are known as autotrophs. Heterotrophic bacteria obtain their nourishment from other living forms.
Ques. What is the composition of rod-shaped bacterial cell walls? (2 marks)
Ans. The bacterial cell wall is made up of a polysaccharide layer called peptidoglycan. This layer protects both Gram-positive and Gram-negative bacterial cells by covering their cytoplasmic membranes.
Ques. Why do bacteria vary in shape? (3 marks)
Ans. The three main forms of bacteria are cocci, spirals, and rods, with the last one being the most prevalent. The variation in the shape of bacteria occurs due to:
- The cell wall made up of peptidoglycan structure, in turn, significantly determines its overall shape.
- Actin-like proteins are important in helping bacteria like B. subtilis and E. coli maintain their rod-like shapes.
Ques. What are some diseases caused by bacteria? (2 marks)
Ans. Bacteria cause a wide range of diseases in humans. Human bacterial infections include typhoid, tetanus, pneumonia, and tuberculosis. Bacterial diseases are contagious and can be transmitted from one person to another. Overall, the four main ways that bacteria can spread are by:
- Touch,
- Airborne Droplets,
- Vectors, and
- Fluids.
Ques. What are bacteriophages? (2 marks)
Ans. A virus that enters bacterial cells and multiplies there is known as a bacteriophage. Their morphology and genetic makeup differ greatly. RNA or DNA can be found within a bacteriophage. There are four to several thousand genes. Viruses known as bacteriophages are able to infect and destroy bacteria without harming human or animal cells.
Ques. What is more damaging: Gram-positive or Gram-negative? (2 marks)
Ans. In comparison to gram-positive bacteria, gram-negative bacteria are more dangerous. This is so because gram-negative bacteria are more resistant to drugs and therefore more difficult to kill due to their hard, impenetrable outer shell.
Ques. Which is the most common example of rod-shaped bacteria? (3 marks)
Ans. One of the most well-known rod-shaped bacteria is likely Escherichia coli, or E. coli.
- Most strains of E. Coli that are typically seen in the intestinal tract of healthy people are completely safe.
- On the other hand, some strains have the potential to cause a variety of diseases, such as respiratory conditions, urinary tract infections, and diarrhoea.
Ques. What are the major differences between gram positive and gram negative bacteria? (2 marks)
Ans. The major differences between gram positive and gram negative bacteria are as follows:
| Gram Positive Bacteria | Gram Negative Bacteria |
|---|---|
| Thick peptidoglycan layer | Thin peptidoglycan layer |
| Presence of Techoic and Lipoteichoic acid | Presence of Lipopolysaccharides |
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