विस्तृत व्याख्या:

Biocontrol Antibiotics Produced by Antagonistic Rhizobacteria (जैव-नियंत्रण जीवाणु एवं उनके एंटीबायोटिक्स):

• 2, 4-diacetyl-phloroglucinol (DAPG): A broad-spectrum phenolic antibiotic produced by plant-growth promoting fluorescent pseudomonads (Pseudomonas fluorescens / P. protegens), responsible for natural suppression of take-all disease of wheat caused by Gaeumannomyces graminis $\rightarrow$ (I).
• Herbicolin (Herbicolin A & B): Lipopeptide antibiotics synthesized by Pantoea agglomerans (formerly Erwinia herbicola), effective against phytopathogenic fungi and fire blight $\rightarrow$ (II).
• Zwittermicin A: An aminopolyol antibiotic produced by Bacillus cereus (strain UW85), known for suppressing damping-off caused by Phytophthora medicaginis and Pythium $\rightarrow$ (III).
• Xanthobaccin A: A macrocyclic lactam antibiotic isolated from Lysobacter sp. (e.g., Lysobacter enzymogenes strain SB-K88) showing potent antifungal activity against sugar beet damping-off (Aphanomyces cochlioides) $\rightarrow$ (IV).

Matching sequence: (A) - (I), (B) - (II), (C) - (III), (D) - (IV).
Correct Answer: Option 2.

विस्तृत व्याख्या:

Bacterial Ingress and Mode of Infection (जीवाणु संक्रमण की विधि):

• Statement (I) is CORRECT: Plant pathogenic bacteria lack the mechanical force to breach the intact plant cuticle directly. They can only enter host plant tissues through natural openings (such as stomata, hydathodes, lenticels, nectaries) or through mechanical wounds (caused by cultivation, hail, pruning, or insect feeding).
• Statement (II) is CORRECT: Unlike phytopathogenic fungi that differentiate specialized morphological infection structures (such as appressoria, penetration pegs, and haustoria), bacteria enter passively as individual cells suspended in water films without producing specialized morphological penetration structures.

विस्तृत व्याख्या:

Bacterial Cell Envelope and Membrane Architecture (जीवाणु कोशिका झिल्ली संरचना):

• Statement (I) is CORRECT: The inner cytoplasmic membrane of all eubacteria is a symmetrical phospholipid bilayer (predominantly phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin) intercalated with proteins.
• Statement (II) is CORRECT: Gram-negative bacteria possess an asymmetric outer membrane: the inner leaflet is composed of standard phospholipids, whereas the outer leaflet is composed of complex lipopolysaccharides (LPS / endotoxin) consisting of Lipid A, core polysaccharide, and O-antigen side chains.

विस्तृत व्याख्या:

Microbiology of Yogurt Production (योगर्ट स्टार्टर कल्चर):

• Traditional commercial yogurt is produced by the synergistic proto-cooperative symbiotic activity of two specific thermophilic lactic acid bacteria:

• Streptococcus thermophilus (C)
• Lactobacillus delbrueckii subsp. bulgaricus (syn. Lactobacillus bulgaricus) (D)
  • S. thermophilus rapidly produces acid and lowers pH, stimulating L. bulgaricus, which produces acetaldehyde (providing characteristic yogurt aroma) and releases amino acids/peptides.

• Bacillus cereus is an opportunistic food poisoning pathogen and B. amyloliquefaciens produces industrial amylases; neither is a yogurt starter culture.