🔬 Kingdom Monera: The World of Bacteria 🦠
Understanding Kingdom Monera
Kingdom Monera comprises organisms that are prokaryotic, meaning they lack a true nucleus and other membrane-bound organelles. Bacteria are the sole members of this kingdom and are the most abundant microorganisms on Earth.
Assertion: Bacteria show the most extensive metabolic diversity.
Reason: They can be autotrophic (photosynthetic or chemosynthetic) or heterotrophic (saprophytic or parasitic), adapting to a wide range of environments and nutrient sources.
- Cell Type: All members are prokaryotic.
- Habitat: Found almost everywhere, including extreme habitats like hot springs, deserts, snow, and deep oceans. Many are also parasites.
- Metabolic Diversity: Exhibit the most extensive metabolic diversity within the living world. Some are autotrophic (chemosynthetic or photosynthetic), while the vast majority are heterotrophs (depending on other organisms or dead organic matter).
- Reproduction: Primarily reproduce by fission. Under unfavorable conditions, they can produce spores. They also show a primitive type of DNA transfer (sexual reproduction).
- Shapes: Grouped into four categories based on shape:
- Coccus (pl.: cocci): Spherical
- Bacillus (pl.: bacilli): Rod-shaped
- Vibrium (pl.: vibrio): Comma-shaped
- Spirillum (pl.: spirilla): Spiral
🔬 Divisions within Kingdom Monera 🔬
1. Archaebacteria
Assertion: Archaebacteria can survive in extremely harsh habitats.
Reason: They possess a unique cell wall structure that differs from other bacteria, enabling their survival in extreme conditions.
- Specialized Habitat: Live in some of the most harsh habitats.
- Types based on habitat:
- Halophiles: Extreme salty areas.
- Thermoacidophiles: Hot springs.
- Methanogens: Marshy areas.
- Unique Feature: Differ from other bacteria in having a different cell wall structure, which is key to their survival in extreme conditions.
- Methanogens Significance: Present in the gut of several ruminant animals (cows, buffaloes) and are responsible for methane (biogas) production from their dung.
🧠 Test Your Knowledge: Archaebacteria! 🧠
Click on a card to reveal the answer.
What is the key difference in cell structure that allows Archaebacteria to survive in extreme conditions?
They have a different cell wall structure compared to other bacteria.
Which type of Archaebacteria thrives in extremely salty environments?
Halophiles.
What is the common name for Archaebacteria found in hot springs?
Thermoacidophiles.
What important gas do Methanogens produce from the dung of ruminant animals?
Methane (biogas).
Are Archaebacteria prokaryotic or eukaryotic?
They are prokaryotic.
Where are Methanogens typically found in ruminant animals?
In their gut.
Can Archaebacteria survive in deep oceans?
Yes, some can live in extreme habitats including deep oceans.
Do Archaebacteria have a nuclear membrane?
No, as prokaryotes, they lack a nuclear membrane.
What is the primary mode of reproduction for Archaebacteria?
Mainly by fission.
Are Archaebacteria considered 'true bacteria'?
No, they are a distinct group from Eubacteria ('true bacteria').
What is the significance of methane production by Methanogens?
It's a source of biogas and contributes to greenhouse gases.
Can Archaebacteria be parasitic?
While the text focuses on their extreme habitats, some bacteria can be parasitic, but it's not a defining characteristic for Archaebacteria mentioned here.
Do Archaebacteria have membrane-bound organelles?
No, as prokaryotes, they lack membrane-bound organelles.
How do Archaebacteria differ metabolically from photosynthetic bacteria?
Many Archaebacteria are chemosynthetic, using chemical reactions for energy, unlike photosynthetic bacteria that use light.
Are Archaebacteria more ancient than Eubacteria?
Their name "Archaebacteria" (ancient bacteria) suggests they are evolutionarily very old, distinct from Eubacteria.
Do Archaebacteria form spores under unfavorable conditions?
The general Monera section mentions spore formation, so it's a possibility, but not explicitly stated for Archaebacteria.
What kind of environment would a thermoacidophile prefer?
Hot and acidic environments, like hot springs.
Are Archaebacteria typically larger or smaller than eukaryotic cells?
As prokaryotes, they are generally smaller than eukaryotic cells.
Do Archaebacteria have plasmids?
The general prokaryotic cell description mentions plasmids in bacteria, so it's possible.
How do Archaebacteria contribute to the carbon cycle?
Methanogens contribute by producing methane, a carbon-containing gas.
2. Eubacteria ('True Bacteria')
Assertion: Heterotrophic bacteria are the most abundant in nature.
Reason: They play a crucial role as decomposers, breaking down dead organic matter and recycling nutrients in ecosystems.
Assertion: Chemosynthetic autotrophic bacteria are important for nutrient recycling.
Reason: They oxidize inorganic substances to produce energy, thereby playing a significant role in biogeochemical cycles of elements like nitrogen, phosphorus, iron, and sulfur.
- Defining Features: Characterized by the presence of a rigid cell wall, and if motile, a flagellum.
- Metabolic Roles:
- Chemosynthetic Autotrophic Bacteria: Oxidize various inorganic substances (nitrates, nitrites, ammonia) to produce ATP. Play a great role in recycling nutrients like nitrogen, phosphorus, iron, and sulfur.
- Heterotrophic Bacteria: Most abundant in nature, majority are important decomposers.
- Economic Importance (Heterotrophic):
- Making curd from milk.
- Production of antibiotics.
- Fixing nitrogen in legume roots (e.g., *Rhizobium*).
- Pathogenic Forms: Some are pathogens causing damage to human beings, crops, farm animals, and pets. Examples include cholera, typhoid, tetanus, citrus canker.
🧠 Test Your Knowledge: Eubacteria! 🧠
Click on a card to reveal the answer.
What is a key characteristic of Eubacteria's cell wall?
They have a rigid cell wall.
How do chemosynthetic autotrophic bacteria produce ATP?
By oxidizing various inorganic substances like nitrates, nitrites, and ammonia.
What is the primary ecological role of most heterotrophic bacteria?
They are important decomposers.
Name one economic use of heterotrophic bacteria.
Making curd from milk, production of antibiotics, or fixing nitrogen in legume roots.
Give an example of a disease caused by pathogenic bacteria.
Cholera, typhoid, tetanus, or citrus canker.
What structure is used by motile Eubacteria for movement?
A flagellum.
What type of metabolism is involved in the recycling of nitrogen, phosphorus, iron, and sulfur by bacteria?
Chemosynthetic autotrophic metabolism.
Are Eubacteria unicellular or multicellular?
They are unicellular prokaryotes.
How do Eubacteria reproduce primarily?
Mainly by fission.
Can Eubacteria form spores?
Yes, sometimes under unfavorable conditions.
What is the role of *Rhizobium* bacteria in agriculture?
Fixing nitrogen in legume roots.
Do Eubacteria have a well-defined nucleus?
No, as prokaryotes, they lack a well-defined nucleus.
What is the term for bacteria that depend on dead organic matter for food?
Saprophytic heterotrophs.
Can Eubacteria transfer DNA between organisms?
Yes, by a primitive type of DNA transfer (sexual reproduction).
What is the shape of a 'bacillus' bacterium?
Rod-shaped.
What is the shape of a 'coccus' bacterium?
Spherical.
What is the shape of a 'vibrio' bacterium?
Comma-shaped.
What is the shape of a 'spirillum' bacterium?
Spiral.
Are Eubacteria typically larger or smaller than eukaryotic cells?
They are generally smaller.
What is the role of Eubacteria in the nitrogen cycle?
Chemosynthetic autotrophs recycle nitrogen compounds, and some heterotrophs like *Rhizobium* fix atmospheric nitrogen.
3. Cyanobacteria (Blue-Green Algae)
Assertion: Cyanobacteria are photosynthetic autotrophs.
Reason: They possess chlorophyll 'a' which is similar to green plants, enabling them to synthesize their own food using light energy.
Assertion: Cyanobacteria often form blooms in polluted water bodies.
Reason: Nutrient enrichment in polluted water provides favorable conditions for their rapid multiplication, leading to dense surface growth.
- Pigment: Have chlorophyll 'a' similar to green plants.
- Mode of Nutrition: Photosynthetic autotrophs.
- Forms: Unicellular, colonial, or filamentous.
- Habitat: Freshwater, marine, or terrestrial.
- Colonies: Often surrounded by a gelatinous sheath.
- Blooms: Can form blooms in polluted water bodies.
- Nitrogen Fixation: Some can fix atmospheric nitrogen in specialized cells called heterocysts (e.g., Nostoc and Anabaena).
🧠 Test Your Knowledge: Cyanobacteria! 🧠
Click on a card to reveal the answer.
What type of chlorophyll do Cyanobacteria possess?
Chlorophyll 'a', similar to green plants.
What is the mode of nutrition for Cyanobacteria?
Photosynthetic autotrophs.
Name the specialized cells in some Cyanobacteria that fix atmospheric nitrogen.
Heterocysts.
What is the gelatinous covering around Cyanobacteria colonies called?
A gelatinous sheath.
Give an example of a filamentous blue-green alga.
Nostoc or Anabaena.
Can Cyanobacteria be found in marine environments?
Yes, they can be freshwater, marine, or terrestrial.
What phenomenon do Cyanobacteria sometimes cause in polluted water bodies?
They often form blooms.
Are Cyanobacteria prokaryotic or eukaryotic?
They are prokaryotic.
Do Cyanobacteria have a true nucleus?
No, as prokaryotes, they lack a true nucleus.
What is another common name for Cyanobacteria?
Blue-green algae.
How do Cyanobacteria contribute to oxygen production on Earth?
As photosynthetic autotrophs, they release oxygen during photosynthesis.
Are Cyanobacteria unicellular, colonial, or filamentous?
They can be unicellular, colonial, or filamentous.
Do Cyanobacteria have a cell wall?
Yes, as bacteria, they possess a cell wall.
What is the main function of the gelatinous sheath around Cyanobacteria colonies?
It provides protection and helps in forming colonies.
How do Cyanobacteria reproduce?
Primarily by fission.
Are Cyanobacteria considered 'algae' in modern classification?
No, though historically called 'blue-green algae', they are now classified under Kingdom Monera due to their prokaryotic nature.
What is the significance of nitrogen fixation by Cyanobacteria?
It converts atmospheric nitrogen into usable forms, enriching soil fertility.
Do Cyanobacteria have flagella for motility?
Most are non-motile, though some filamentous forms can exhibit gliding movement.
What is the role of Cyanobacteria in pioneer communities?
They are often pioneer organisms in barren environments, contributing to soil development.
How do Cyanobacteria contribute to aquatic ecosystems?
They are primary producers and nitrogen fixers, forming the base of many aquatic food webs.
4. Mycoplasma
Assertion: Mycoplasma are the smallest known living cells.
Reason: They completely lack a cell wall and can survive without oxygen, allowing them to be extremely small and adaptable.
Assertion: Mycoplasma are often pathogenic.
Reason: Their lack of a cell wall makes them resistant to many common antibiotics that target cell wall synthesis, making them difficult to treat in infections.
- Cell Wall: Organisms that completely lack a cell wall.
- Size: They are the smallest living cells known (around 0.3 µm in length).
- Oxygen Requirement: Can survive without oxygen.
- Pathogenicity: Many are pathogenic in animals and plants.
- Also known as: PPLO (Pleuro Pneumonia Like Organisms).
🧠 Test Your Knowledge: Mycoplasma! 🧠
Click on a card to reveal the answer.
What is the most distinctive feature of Mycoplasma regarding their cell structure?
They completely lack a cell wall.
What is the approximate size of Mycoplasma, making them the smallest known living cells?
Around 0.3 µm in length.
Can Mycoplasma survive in the absence of oxygen?
Yes, they can survive without oxygen.
Are Mycoplasma typically harmless or pathogenic?
Many are pathogenic in animals and plants.
What does PPLO stand for?
Pleuro Pneumonia Like Organisms.
Why are Mycoplasma resistant to antibiotics like penicillin?
Because penicillin targets cell wall synthesis, which Mycoplasma lack.
Do Mycoplasma have a rigid shape?
No, due to the absence of a cell wall, they are pleomorphic (can change shape).
Are Mycoplasma prokaryotic or eukaryotic?
They are prokaryotic.
Do Mycoplasma have a well-defined nucleus?
No, as prokaryotes, they lack a well-defined nucleus.
How do Mycoplasma reproduce?
Primarily by binary fission.
Can Mycoplasma cause respiratory infections in humans?
Yes, *Mycoplasma pneumoniae* causes atypical pneumonia.
Do Mycoplasma have flagella for motility?
No, they are generally non-motile or exhibit gliding motility.
Are Mycoplasma sensitive to osmotic lysis?
Yes, due to the absence of a rigid cell wall, they are susceptible to osmotic changes.
What is the significance of Mycoplasma being able to survive without oxygen?
It means they can be anaerobic or facultative anaerobic.
Do Mycoplasma have ribosomes?
Yes, as living cells, they have ribosomes (70S) for protein synthesis.
What kind of diseases do Mycoplasma cause in plants?
They can cause various plant diseases, often leading to yellowing and stunted growth.
Are Mycoplasma able to pass through bacterial filters?
Yes, due to their small size, they can pass through filters that retain most bacteria.
Do Mycoplasma have a distinct shape like cocci or bacilli?
No, their lack of a cell wall gives them an irregular or pleomorphic shape.
What is the primary mode of nutrition for Mycoplasma?
They are generally heterotrophic, often parasitic.
How do Mycoplasma differ from viruses in terms of cellularity?
Mycoplasma are cellular organisms (though very simple), while viruses are acellular.
🔬 Prokaryotic Cell Structure: A Closer Look (Based on Chapter 8.4) 🔬
The organization of a prokaryotic cell is fundamentally similar across different shapes and functions, despite their apparent simplicity.
Assertion: Prokaryotic cells lack membrane-bound organelles.
Reason: Their cellular organization is simpler than eukaryotes, and functions typically performed by organelles are often carried out by specialized regions of the cytoplasm or cell membrane.
- General Characteristics:
- Generally smaller than eukaryotic cells.
- Multiply more rapidly than eukaryotic cells.
- Lack a well-defined nucleus.
- Cell Envelope and its Modifications:
Assertion: The cell wall determines the shape of bacterial cells.
Reason: It provides a strong structural support that prevents the bacterium from bursting or collapsing due to osmotic pressure.
Assertion: Mesosomes are important for DNA replication in prokaryotes.
Reason: These specialized extensions of the plasma membrane help in DNA replication and its distribution to daughter cells during cell division.
- Chemically complex three-layered structure:
- Glycocalyx: Outermost layer. Can be a loose slime layer in some, or a thick, tough capsule in others.
- Cell Wall: Determines the shape of the cell and provides strong structural support to prevent bursting or collapsing.
- Plasma Membrane: Selectively permeable, interacts with the outside world. Structurally similar to eukaryotic plasma membranes.
- Gram Staining: Bacteria are classified as Gram positive (take up Gram stain) or Gram negative (do not take up Gram stain) based on cell envelope differences.
- Mesosome: A specialized differentiated form of cell membrane extension into the cell (vesicles, tubules, lamellae). Helps in cell wall formation, DNA replication, distribution to daughter cells, respiration, secretion, increasing surface area, and enzymatic content.
- Chromatophores: Other membranous extensions into the cytoplasm in some prokaryotes (like cyanobacteria) that contain pigments.
- Chemically complex three-layered structure:
- Genetic Material:
Assertion: Prokaryotic genetic material is naked.
Reason: It is not enveloped by a nuclear membrane, unlike eukaryotic DNA which is enclosed within a nucleus.
Assertion: Plasmids confer unique phenotypic characters to bacteria.
Reason: They carry genes for traits like antibiotic resistance, which are not part of the main genomic DNA but provide adaptive advantages.
- Naked DNA: The genetic material is basically naked, not enveloped by a nuclear membrane.
- Genomic DNA: A single chromosome/circular DNA.
- Plasmids: Small circular DNA outside the genomic DNA, conferring unique phenotypic characters (e.g., antibiotic resistance).
- Locomotory Structures:
Assertion: Bacterial flagella are structurally different from eukaryotic flagella.
Reason: Bacterial flagella are simpler, composed of three parts (filament, hook, basal body), and lack the 9+2 microtubule arrangement found in eukaryotic flagella.
Assertion: Pili and fimbriae do not play a role in bacterial motility.
Reason: Their primary functions are attachment to surfaces (rocks, host tissues) and facilitating conjugation (DNA transfer), not propulsion.
- Flagella: Thin filamentous extensions from their cell wall, responsible for motility. Composed of filament, hook, and basal body.
- Pili: Elongated tubular structures made of a special protein; do not play a role in motility.
- Fimbriae: Small bristle-like fibers sprouting out of the cell; help attach bacteria to rocks in streams and host tissues.
- Ribosomes and Inclusion Bodies:
Assertion: Prokaryotic ribosomes are 70S type.
Reason: They are composed of two subunits, 50S and 30S, which together form the 70S ribosome, distinct from the larger 80S ribosomes found in eukaryotes.
Assertion: Inclusion bodies in prokaryotes are not membrane-bound.
Reason: They are simply reserve material stored freely in the cytoplasm, unlike organelles which are enclosed by membranes.
- Ribosomes: Associated with the plasma membrane, 70S type (composed of 50S and 30S subunits). Site of protein synthesis. Several ribosomes can form a chain called polyribosomes or polysome.
- Inclusion Bodies: Reserve material stored in the cytoplasm, not bound by any membrane system. Examples: phosphate granules, cyanophycean granules, glycogen granules.
- Gas Vacuoles: Found in blue-green, purple, and green photosynthetic bacteria.
- Organelles: Lack membrane-bound organelles found in eukaryotic cells, except for ribosomes.
🧠 Test Your Knowledge: Prokaryotic Cell Structure! 🧠
Click on a card to reveal the answer.
What are the three layers of the prokaryotic cell envelope from outermost to innermost?
Glycocalyx, Cell Wall, Plasma Membrane.
What is the function of the cell wall in prokaryotes?
Determines shape and provides structural support to prevent bursting/collapsing.
What are mesosomes formed from?
Extensions of the plasma membrane into the cell.
What type of genetic material is found in prokaryotes?
Naked, circular DNA (genomic DNA) and plasmids.
What is the function of plasmids in bacteria?
Confer unique phenotypic characters, like antibiotic resistance.
What are the three parts of a bacterial flagellum?
Filament, hook, and basal body.
What is the primary function of fimbriae?
To help bacteria attach to surfaces (rocks, host tissues).
What type of ribosomes are found in prokaryotes?
70S ribosomes.
Are inclusion bodies membrane-bound organelles?
No, they are not bound by any membrane system.
Give an example of an inclusion body.
Phosphate granules, cyanophycean granules, or glycogen granules.
What is the difference between a slime layer and a capsule (types of glycocalyx)?
A slime layer is loose, while a capsule is thick and tough.
What is the primary site of protein synthesis in prokaryotic cells?
Ribosomes.
How do prokaryotic cells differ from eukaryotic cells in terms of nuclear organization?
Prokaryotes lack a well-defined nucleus and nuclear membrane.
What are chromatophores, and where are they found?
Membranous extensions containing pigments, found in some prokaryotes like cyanobacteria.
What is a polysome?
A chain formed when several ribosomes attach to a single mRNA molecule.
Do prokaryotic cells have a cytoskeleton?
The text doesn't explicitly mention a cytoskeleton for prokaryotes, which are simpler in internal organization compared to eukaryotes.
How does the plasma membrane of prokaryotes compare to eukaryotes?
It is structurally similar and selectively permeable.
What is the significance of gas vacuoles in photosynthetic bacteria?
They provide buoyancy control, allowing bacteria to position themselves optimally for light absorption.
What is the main difference in size between prokaryotic and eukaryotic cells?
Prokaryotic cells are generally smaller (e.g., 1-2 µm for typical bacteria) than eukaryotic cells (e.g., 10-20 µm).
How does Gram staining help in classifying bacteria?
It differentiates bacteria into Gram-positive or Gram-negative based on cell envelope differences, which influences antibiotic treatment.
🏥 Bacterial Diseases, Vaccines, and Tests 🏥
Common Bacterial Human Diseases (15 Examples)
- Typhoid (Salmonella typhi)
- Tuberculosis (TB) (Mycobacterium tuberculosis)
- Cholera (Vibrio cholerae)
- Tetanus (Clostridium tetani)
- Pneumonia (Streptococcus pneumoniae, Haemophilus influenzae)
- Diphtheria (Corynebacterium diphtheriae)
- Whooping Cough (Pertussis) (Bordetella pertussis)
- Plague (Yersinia pestis)
- Leprosy (Mycobacterium leprae)
- Syphilis (Treponema pallidum)
- Gonorrhea (Neisseria gonorrhoeae)
- Anthrax (Bacillus anthracis)
- Bacterial Meningitis (e.g., Neisseria meningitidis, Streptococcus pneumoniae)
- Food Poisoning (e.g., Staphylococcus aureus, Clostridium botulinum, E. coli)
- Urinary Tract Infections (UTIs) (e.g., Escherichia coli)
Vaccines for Bacterial Diseases
Vaccination is a crucial strategy for preventing bacterial infections. Some notable bacterial vaccines include:
- DTaP/Tdap Vaccine: Protects against Diphtheria, Tetanus, and Pertussis (Whooping Cough).
- BCG Vaccine: Used for Tuberculosis (TB), particularly in high-incidence areas.
- Pneumococcal Vaccine: Protects against diseases caused by Streptococcus pneumoniae, such as pneumonia, meningitis, and sepsis.
- Typhoid Vaccine: Available in injectable and oral forms for Typhoid fever.
- Meningococcal Vaccine: Protects against bacterial meningitis caused by *Neisseria meningitidis*.
- Cholera Vaccine: Available for Cholera, especially for travelers to endemic areas.
Diagnostic Tests for Bacterial Diseases
Accurate diagnosis is essential for effective treatment of bacterial infections. Common diagnostic tests include:
- Widal Test: Used for the diagnosis of Typhoid fever, detecting antibodies against *Salmonella typhi*.
- Mantoux Test (Tuberculin Skin Test): A screening test for Tuberculosis (TB) infection, detecting a delayed-type hypersensitivity reaction.
- Gram Stain: A differential staining technique used to classify bacteria into Gram-positive or Gram-negative based on their cell wall properties, crucial for guiding antibiotic selection.
- Culture and Sensitivity Tests: Involves growing bacteria from a patient sample (e.g., blood, urine, sputum) to identify the specific pathogen and determine its susceptibility to various antibiotics.
- PCR (Polymerase Chain Reaction): Molecular test to detect bacterial DNA directly in samples, offering rapid and highly sensitive diagnosis.
- ELISA (Enzyme-Linked Immunosorbent Assay): Used to detect bacterial antigens or antibodies in patient samples for various bacterial diseases.
💡 Did You Know? Click to Reveal! 💡
The human body contains more bacterial cells than human cells! While the exact ratio is debated, it's estimated that bacteria outnumber human cells by a factor of at least 1.3:1, highlighting the vast and often beneficial microbial world within us.