Monera (Prokaryotes) Questions in English

(B) Whittaker's $(1969)$ classification system classifies organisms into five kingdoms: Monera,Protista,Fungi,Plantae,and Animalia.
Non-nucleated organisms are prokaryotes,which lack a defined nucleus and membrane-bound organelles.
Kingdom Monera consists exclusively of unicellular prokaryotic organisms,such as bacteria.
Therefore,the non-nucleated,unicellular organisms are included in the kingdom Monera.

(B) The five-kingdom classification system was proposed by $R.H. Whittaker$.
In this system,the kingdom $Monera$ is the only kingdom that consists of all prokaryotic organisms,such as bacteria and cyanobacteria.
$Protista$ consists of eukaryotic unicellular organisms,while $Myxophyceae$ and $Myxomycophyta$ are not considered separate kingdoms in this classification.

(A) The correct answer is $A$ (Monera).
Kingdom Monera includes bacteria,which exhibit a wide range of nutritional modes.
Some bacteria are photoautotrophs,such as green sulphur bacteria,which use light energy to synthesize food.
Some are chemoautotrophs,such as $Nitrosomonas$,which derive energy from the oxidation of inorganic chemical substances.
Most bacteria are heterotrophs,such as $Bacillus$ $sp.$,which obtain nutrients from organic matter.

(B) Biochemical characteristics,such as cell wall composition,metabolic pathways,and ribosomal $RNA$ sequences,are primarily used for the classification and identification of members of the kingdom $Monera$. Since members of $Monera$ (bacteria) are morphologically simple and lack complex cellular structures,biochemical and molecular markers are essential for distinguishing between different species and strains.

(A) Actinomycetes are filamentous bacteria that possess a prokaryotic cellular organization. In the five-kingdom classification system proposed by $R$.$H$. Whittaker,all prokaryotic organisms are placed under the kingdom $Monera$. Therefore,actinomycetes are included in kingdom $Monera$.

(A) The five kingdom system of classification was proposed by $R.H. Whittaker$.
According to this system,all prokaryotic organisms are placed under the kingdom $Monera$.
Blue-green algae (cyanobacteria),nitrogen-fixing bacteria,and methanogenic archaebacteria are all prokaryotic organisms.
Therefore,they are all included in the kingdom $Monera$.

(C) Barophilic prokaryotes,also known as piezophiles,are microorganisms that thrive at high hydrostatic pressures.
These organisms are typically found in deep-sea environments,such as deep marine sediments or ocean trenches,where the pressure is significantly higher than at the surface.
They have specialized cellular structures and enzymes that allow them to function optimally under extreme pressure conditions.

(B) The 'flower distortion' or 'witches' broom' type symptoms in plants like carrot and onion are typically caused by $Mycoplasma$ (now classified under $Phytoplasma$).
$Mycoplasma$ are wall-less prokaryotes that infect the phloem of plants,leading to abnormal growth patterns,including the distortion of floral parts.

(B) Cotton stenosis,also known as the 'little leaf' disease of cotton,is caused by $Mycoplasma$ (specifically $Phytoplasma$).
$Mycoplasma$ are wall-less prokaryotes that infect the phloem tissue of plants,leading to symptoms such as stunted growth,yellowing,and the formation of small,clustered leaves.

(A) Certain bacteria,such as green sulfur bacteria and purple sulfur bacteria,do not possess chlorophyll-$a$ (which is found in plants and cyanobacteria).
Instead,they contain bacteriochlorophyll,which allows them to perform photosynthesis using hydrogen sulfide $(H_2S)$ or other organic compounds as electron donors instead of water $(H_2O)$.
Therefore,these organisms are capable of photosynthesis without typical chlorophyll.

(D) Bacteria were first observed and described by $A.V. Leeuwenhoek$ in $1676$. He referred to these microscopic organisms as 'animalcules'. Therefore,the correct answer is $A.V. Leeuwenhoek$.

(A) In the early systems of classification,organisms were primarily classified based on the presence or absence of a cell wall. Since bacteria possess a rigid cell wall,similar to plants,they were historically grouped with plants. However,modern classification systems place bacteria in the kingdom $Monera$ due to their prokaryotic cellular organization.

(C) Bacteria are prokaryotic organisms. They lack a well-defined nucleus. Their genetic material consists of $DNA$,which is typically double-stranded and circular. This $DNA$ is located in a specific region of the cytoplasm known as the nucleoid. Therefore,option $C$ is the correct statement.

(C) The bacterial cell wall is primarily composed of peptidoglycan,also known as murein.
Peptidoglycan consists of a sugar backbone made of alternating $N$-acetylglucosamine $(NAG)$ and $N$-acetylmuramic acid $(NAM)$ residues,which are cross-linked by short chains of amino acids (peptides).
Therefore,the chief components are amino acids and polysaccharides (sugars).
Thus,option $C$ is the correct answer.

(A) Bacteria are classified into four basic shapes based on their morphology:
$1$. $Cocci$ are spherical or oval-shaped bacteria.
$2$. $Bacilli$ are rod-shaped bacteria.
$3$. $Vibrio$ are comma-shaped or curved bacteria.
$4$. $Spirilli$ are spiral-shaped bacteria.
Therefore,the bacteria with a comma shape are called $Vibrio$.

(B) The primary difference between Gram-positive $(G+)$ and Gram-negative $(G-)$ bacteria is found in their cell wall structure.
In $G+$ bacteria,the cell wall is $200-300 \ \mathring{A}$ thick,consisting of approximately $85\%$ mucopeptides (peptidoglycan) and $1-2\%$ lipids.
In contrast,the cell wall of $G-$ bacteria is $100-200 \ \mathring{A}$ thick,containing only $10-12\%$ mucopeptides and a significantly higher lipid content of $80-90\%$.

(A) The cell wall of bacteria is composed of peptidoglycan,also known as murein.
Peptidoglycan consists of a polymer of sugars and amino acids.
The sugar component is made up of alternating residues of $N$-acetylglucosamine $(NAG)$ and $N$-acetylmuramic acid $(NAM)$.
Muramic acid is a characteristic component of the bacterial cell wall and is not found in the cell walls of fungi (like yeast and Rhizopus) or algae.

(B) Chemosynthetic bacteria are autotrophic organisms that do not rely on sunlight for energy. Instead,they synthesize their food by oxidizing various inorganic compounds such as ammonia,nitrites,or sulfides. This process releases energy,which is then used to fix carbon dioxide into organic molecules.

(A) Bacteria are classified based on the arrangement of flagella on their surface.
$1$. $Peritrichous$: Bacteria that have flagella distributed all over their body surface.
$2$. $Atrichous$: Bacteria that lack flagella entirely.
$3$. $Monotrichous$: Bacteria that have a single flagellum at one end.
$4$. $Cephalotrichous$: Bacteria that have a tuft of flagella at one end.
Therefore,bacteria with flagella all over the body are called $Peritrichous$.

(B) $E. coli$ (Escherichia coli) is a type of bacterium that normally lives in the intestines of people and animals.
It is a primary inhabitant of the human colon (large intestine),where it helps in the production of Vitamin $K$ and Vitamin $B$ complex.
Therefore,the correct habitat among the given options is the colon.

(A) The nuclear material of bacteria,which consists of a naked $DNA$ molecule,is identified as a nucleoid.
Prokaryotic cells,such as those found in bacteria,lack a well-defined membrane-bound nucleus.
Instead,their genetic material is organized in a region called the nucleoid.

(D) $Spirillum \text{ } volutans$ is considered one of the largest known bacteria.
It is a large, motile, spiral-shaped bacterium that can reach lengths of up to $60 \text{ } \mu m$ and has a diameter of $1.4-1.7 \text{ } \mu m$.
Due to its significant size compared to typical bacteria, it is easily visible under a light microscope.

(A) Purple sulphur bacteria are photosynthetic organisms that use light energy to synthesize organic compounds. They use inorganic compounds like $H_2S$ as electron donors instead of water. Since they use light as an energy source and inorganic compounds as electron donors,they are classified as $Photolithotrophs$.

(C) Bacteria are classified based on their shape. $Cocci$ are spherical-shaped bacteria.
- $Diplococci$ occur in pairs.
- $Streptococci$ occur in chains.
- $Staphylococci$ occur in irregular bunches or grape-like clusters.
- $Streptobacilli$ are rod-shaped bacteria arranged in chains.
Therefore,$cocci$ in a bunch are known as $Staphylococci$.

(C) The glycocalyx is a loose,gelatinous,thin sheath known as the slime layer. It is secreted by the protoplast and is primarily composed of polysaccharides. Its main function is to protect the bacterial cell from desiccation (loss of water) and viral attacks.

(A) Chlorobium vesicles are specialized light-harvesting structures found in green sulfur bacteria (e.g.,$Chlorobium$).
These vesicles contain bacteriochlorophyll pigments that allow these organisms to perform photosynthesis in low-light environments.
Therefore,they are characteristic of green bacteria.

(C) An episome is a genetic element that can exist either as a plasmid (independent of the bacterial chromosome) or by integrating into the bacterial chromosome. The $F$ factor (fertility factor) in $E. coli$ is a classic example of an episome,which is also known as the sex factor because it facilitates bacterial conjugation.

(D) Nitrifying bacteria,such as $Nitrosomonas$ and $Nitrobacter$,are classified as chemosynthetic autotrophs.
They manufacture their organic food by utilizing the chemical energy released during the oxidation of inorganic compounds (like ammonia or nitrites).
This process of synthesizing organic compounds using energy derived from chemical reactions is known as chemosynthesis.

(A) The cell membranes of $Archaebacteria$ contain branched-chain lipids (ether-linked lipids).
These unique lipids provide structural stability to the membrane,which allows $Archaebacteria$ to survive in extreme environmental conditions such as high temperature,high salinity,and high acidity.

(D) $Escherichia \ coli$ $(E. \ coli)$ is a prokaryotic bacterium.
Prokaryotes are characterized by having a single circular chromosome,meaning they are haploid $(n)$.
They do not possess a diploid $(2n)$ state.
Transformation and transduction are well-documented methods of horizontal gene transfer in $E. \ coli$.
Many strains of $E. \ coli$ are motile and possess flagella for locomotion.
Therefore,the term 'Diploid' is not applicable to $E. \ coli$.

(D) Bacteria are classified as primitive organisms (prokaryotes) because they lack a well-defined,membrane-bound nucleus. Instead,they contain an incipient nucleus,also known as a nucleoid,where the genetic material is present in a naked state. Furthermore,they reproduce primarily through binary fission,which is a form of amitotic division,rather than the complex mitotic division seen in eukaryotes.

(C) The correct answer is $C$.
During unfavourable environmental conditions,certain bacteria (e.g.,$Clostridium$ $tetani$ and $Bacillus$ $anthracis$) form a highly resistant,dormant structure within the cell known as an endospore.
Endospores are resistant to high temperatures,radiation,desiccation,and chemical disinfectants,allowing the bacteria to survive in extreme conditions for long periods.

(A) $Mycobacterium$ $tuberculosis$ is a rod-shaped bacterium that causes tuberculosis in humans.
Its typical dimensions range from $1$ to $4 \ \mu m$ in length and $0.2$ to $0.6 \ \mu m$ in width.
Among the given options,$0.8 \ \mu m$ is the most representative value for its length in various biological contexts.

(D) $Salmonella$ species are Gram-negative,rod-shaped bacteria.
They possess flagella distributed over the entire surface of the cell body.
Bacteria with flagella distributed all over the cell surface are classified as $Peritrichous$.

(C) Spirochetes are a group of Gram-negative bacteria that have long,helically coiled cells.
They are characterized by their unique corkscrew-like shape,which allows them to move through viscous environments.
Therefore,they are helical in shape.

(D) $Mycobacterium$ is a genus of Actinobacteria,which are gram-positive bacteria.
Despite their name,which implies a fungal-like appearance,they do not form a true mycelium.
They are unicellular prokaryotic organisms and do not possess the filamentous,branching structures known as mycelium found in fungi or some other actinomycetes.
Therefore,none of the given options are correct.

(B) Myxobacteria,also known as slime bacteria,are a group of bacteria that predominantly live in the soil.
They lack flagella and are unable to swim in liquid media.
Instead,they exhibit a unique form of motility known as gliding motility,which allows them to move across solid surfaces by secreting slime.

(A) $Thiobacillus$ $ferrooxidans$ is a chemoautotrophic bacterium.
It obtains energy by oxidizing inorganic compounds.
Specifically,it oxidizes ferrous iron $(Fe^{++})$ to ferric iron $(Fe^{+++})$ to generate energy for its metabolic processes.
Therefore,the correct option is $A$.

(D) Gram-positive bacteria retain the crystal violet stain due to a thick peptidoglycan layer in their cell wall.
$1$. $A$ defective staining technique (e.g.,over-decolorization with alcohol) can wash away the primary stain,making them appear Gram-negative.
$2$. $A$ changed $pH$ of the medium can affect the cell wall integrity or the binding affinity of the dye.
$3$. In an aged bacterial culture,the cell wall structure often degrades or becomes thinner,losing its ability to retain the crystal violet-iodine complex.
Therefore,all these conditions can lead to a Gram-positive bacterium appearing Gram-negative.

(B) $Escherichia coli$ (commonly known as $E. coli$) is a Gram-negative,facultative anaerobic,rod-shaped bacterium.
It is a normal inhabitant of the lower intestine of warm-blooded organisms,including humans and animals.
It plays a significant role in the gut microbiota and is widely used as an indicator organism for fecal contamination in water testing.

(C) Bacteria are prokaryotic organisms. Like all living cells,they contain genetic material in the form of $DNA$ (a nucleic acid) and are composed of various proteins that form their structural components,enzymes,and cellular machinery. Therefore,they are primarily made up of nucleic acids and proteins.

(D) The $R$-factor (Resistance factor) is a specific type of plasmid found in bacteria.
These plasmids carry genes that provide resistance against various antibiotics.
Therefore,genes for antibiotic resistance are located in the plasmid.

(C) The name $Staphylococcus$ is derived from the Greek word 'staphyle',which means 'a bunch of grapes'. These bacteria are spherical (cocci) and divide in multiple planes,resulting in the formation of irregular,grape-like clusters. Therefore,the correct arrangement is an irregular cluster.

(B) Peptidoglycan,also known as murein,is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria,forming the cell wall.
Cyanobacteria are a phylum of bacteria that obtain their energy through photosynthesis and possess a cell wall containing peptidoglycan.
Therefore,both bacteria (eubacteria) and cyanobacteria are characterized by the presence of peptidoglycan in their cell walls.
Archaebacteria lack peptidoglycan in their cell walls,and eukaryotes (like fungi or plants) have cell walls made of chitin or cellulose,respectively.

(B) Bacteria and other organisms belonging to the kingdom $Monera$ are prokaryotic in nature.
Prokaryotic cells are characterized by the absence of membrane-bound organelles such as mitochondria,chloroplasts,endoplasmic reticulum,and a well-defined nucleus.
They do possess ribosomes (of the $70S$ type),a nucleoid (naked genetic material),and a plasma membrane.
Therefore,the correct answer is $B$ (Mitochondria).

(C) Organisms that possess cells but lack a distinct,membrane-bound nucleus are classified as prokaryotes.
Both bacteria and cyanobacteria (blue-green algae) belong to the kingdom Monera and are prokaryotic in nature.
Therefore,both $(a)$ and $(b)$ are correct.

(C) Archaebacteria are unique organisms that differ from other bacteria in their cell wall structure,which allows them to survive in extreme environmental conditions.
Extreme halophiles (salt-loving) are found in extremely salty areas.
Thermoacidophiles (thermophiles) are found in hot springs and hydrothermal vents.
Therefore,the correct answer is Archaebacteria.

(A) The bacterial cell wall is primarily composed of a polymer known as Peptidoglycan (also called murein).
It consists of sugars and amino acids that form a mesh-like layer outside the plasma membrane of most bacteria,providing structural support and protection.