Which of the following statements is/are correct? Viruses can infect 1. bacteria 2. fungi 3. plants Select the correct answer using the code given below.
Contents16
- A1 and 2 only
- B3 only
- C1 and 3 only
- D1, 2 and 3
Show answer
Answer: (D) 1, 2 and 3
Answer: (d) 1, 2 and 3
All three statements are correct — viruses can infect bacteria, fungi, AND plants.
Viruses are the smallest known infectious agents.
They cannot reproduce on their own — they need a host cell to multiply.
They can infect virtually ALL types of living organisms:
Bacteria — YES. Viruses that infect bacteria are called BACTERIOPHAGES (or simply 'phages'). Example: T4 bacteriophage infects E. coli bacteria. Phages are actually the most abundant biological entities on Earth.
Fungi — YES. Viruses that infect fungi are called MYCOVIRUSES. Most mycoviruses have double-stranded RNA (dsRNA) genomes. They can infect yeasts, molds, and mushrooms.
Plants — YES. Many plant viruses cause significant damage to crops worldwide. Example: Tobacco Mosaic Virus (TMV) — the first virus ever discovered (1892). Other examples include Cauliflower Mosaic Virus and Potato Virus Y.
Additionally, viruses also infect:
- Animals (including humans) — e.g., HIV, Influenza, COVID-19
- Archaea — viruses that infect archaea
- Even other viruses — called virophages!
Since all three are correct, the answer is (d) "1, 2 and 3".
This is from NCERT Class XII Biology.
Viruses are obligate parasites that can infect all major forms of life - bacteria, fungi, plants, animals, and even archaea.
Many students incorrectly think viruses only infect animals and humans, missing that bacteriophages are actually the most abundant biological entities on Earth.
The question tests breadth of understanding about viral host range rather than specific virus-disease knowledge.
Viral Host Range & Infection Mechanisms
Science And Technology viruses infect bacteria fungi plants
Viral Host Range: Which Organisms Can Viruses Infect?
Viruses can infect all types of living organisms — bacteria, fungi, plants, animals, and even archaea
Viruses are obligate intracellular parasites — they cannot reproduce without a host cell
Bacteriophages are the most abundant biological entities on Earth
Each virus type has specific host range — they cannot infect just any organism
What Are Viruses
Viruses are the smallest known infectious agents that exist at the boundary between living and non-living matter. They consist of genetic material (DNA or RNA) wrapped in a protein coat called a capsid. Unlike bacteria or fungi, viruses cannot reproduce independently — they are obligate intracellular parasites that hijack the cellular machinery of their host to multiply.
Viral Infections by Host Type
Host Type | Virus Name | Examples | Key Features |
|---|---|---|---|
Bacteria | Bacteriophages (Phages) | T4 phage infects E. coli | Most abundant biological entities on Earth |
Fungi | Mycoviruses | Infect yeasts, molds, mushrooms | Most have double-stranded RNA genomes |
Plants | Plant viruses | Tobacco Mosaic Virus (TMV), Potato Virus Y | First virus discovered was TMV in 1892 |
Animals | Animal viruses | HIV, Influenza, COVID-19, Rabies | Include DNA and RNA viruses |
Archaea | Archaeal viruses | Infect extremophile archaea | Often have unique capsid structures |
Why This Question Matters
The question tests whether students know viruses have a universal host range — they're not limited to animals only
Many students incorrectly think viruses only infect humans and animals, missing bacteria and fungi
All three statements are correct — viruses can indeed infect bacteria, fungi, AND plants
Trap: Assuming viruses only infect animals because most familiar examples (flu, COVID) are animal viruses
Trap: Thinking fungi are too simple to be infected by viruses — mycoviruses do exist
Trap: Confusing viruses with bacteria — viruses infect bacteria (bacteriophages), not the other way around
Remember: TMV was the first virus discovered in 1892 from plants, not animals
Bacteriophages & Bacterial Viruses
Science And Technology bacteria bacteriophages
Bacteriophages: Viruses That Infect Bacteria
Bacteriophages (phages) are viruses that specifically infect bacteria
They are the most abundant biological entities on Earth
Classic example: T4 bacteriophage infects E. coli bacteria
Used in phage therapy as alternatives to antibiotics
Discovery & Significance
Bacteriophages were discovered independently by Frederick Twort (1915) and Félix d'Hérelle (1917). The name 'bacteriophage' literally means 'bacteria eater'. They play crucial roles in controlling bacterial populations in nature and are being researched as phage therapy — using phages to treat antibiotic-resistant bacterial infections.
Lytic Cycle of Bacteriophages
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****Attachment****
Phage binds to specific receptors on bacterial cell surface`"]
s2["`****Penetration****
Phage injects its DNA/RNA into the bacterial cell`"]
s3["`****Replication****
Viral genetic material hijacks bacterial machinery to make copies`"]
s4["`****Assembly****
New viral components assemble into complete phage particles`"]
s5["`****Lysis****
Bacterial cell bursts, releasing new phages to infect other bacteria`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5T4 Bacteriophage Structure
Source: ScienceDirect.com — Bacteriophage - an overview | ScienceDirect Topics · www.sciencedirect.com
Don't confuse: Bacteriophages infect bacteria — not the other way around
Remember: Phages are viruses, not bacteria themselves
T4 phage + E. coli is the classic textbook example to remember
Mycoviruses & Plant Viruses
Science And Technology fungi plants mycoviruses
Viruses Infecting Fungi & Plants: Mycoviruses and Plant Pathogens
Mycoviruses infect fungi — most have double-stranded RNA genomes
Tobacco Mosaic Virus (TMV) was the first virus discovered in 1892
Plant viruses cause significant crop losses worldwide
Mycoviruses can infect yeasts, molds, and mushrooms
Key Differences: Mycoviruses vs Plant Viruses
Feature | Mycoviruses (Fungi) | Plant Viruses |
|---|---|---|
Host | Yeasts, molds, mushrooms | Flowering plants, crops, trees |
Genome | Mostly double-stranded RNA | DNA or RNA (single/double stranded) |
Transmission | Through fungal spores | Insects, mechanical damage, seeds |
Examples | La France disease virus (mushrooms) | TMV, Potato Virus Y, Cauliflower Mosaic Virus |
Discovery | 1960s | 1892 (TMV by Dmitri Ivanovsky) |
Historical Significance
TMV discovery (1892) marked the beginning of virology as a science
TMV was called a 'contagious living fluid' before viruses were understood
Plant viruses helped establish that infectious agents smaller than bacteria exist
Mycoviruses were discovered much later in the 1960s
Tobacco Mosaic Virus
Source: ScienceDirect.com — Tobacco Mosaic Virus - an overview | ScienceDirect Topics · www.sciencedirect.com
Don't assume fungi are 'too simple' for viral infection — mycoviruses do exist
Remember: TMV was discovered in 1892 from plants, not animals
Mycoviruses mostly have dsRNA genomes, unlike most other viruses
Virus Classification & Types
Science And Technology viruses
Classification of Viruses: DNA, RNA & Host-Based Categories
Viruses classified by genome type (DNA/RNA) and host range
Baltimore Classification groups viruses into 7 classes based on genome
Some viruses are host-specific, others have broader ranges
Classification Principles
Viruses are classified using multiple criteria: genome type (DNA or RNA, single or double-stranded), host range (which organisms they infect), capsid structure, and replication strategy. The Baltimore Classification system groups all viruses into seven classes based on how they produce mRNA from their genomes.
Major Virus Categories
# Virus Classification
## By Genome
- DNA viruses
- RNA viruses
- Single-stranded
- Double-stranded
## By Host
- Bacteriophages
- Animal viruses
- Plant viruses
- Mycoviruses
## By Structure
- Enveloped
- Non-enveloped
- Helical capsid
- Icosahedral capsidExamples by Host Type
Host Category | Common Examples | Genome Type | Medical/Agricultural Impact |
|---|---|---|---|
Human/Animal | HIV, Influenza, Rabies | RNA/DNA | Major disease burden |
Plants | TMV, Potato Virus Y | RNA | Crop losses |
Bacteria | T4, Lambda phage | DNA | Phage therapy potential |
Fungi | Mushroom viruses | dsRNA | Limited economic impact |
Don't memorize only animal virus examples — UPSC tests plant and bacterial viruses too
Remember: Viruses need living host cells — they cannot infect dead matter
Host specificity varies — some viruses are very specific, others can cross species