Unusual bacterial reproduction — Reproduction by budding is observed in which of the following bacteria?

Introduction / Context:
Most bacteria reproduce by binary fission, but some lineages use budding, stalked-cell cycles, or asymmetric division. Recognizing these exceptions is important in environmental microbiology and taxonomy because cell cycle morphology affects cultivation strategies, biofilm behavior, and ecological niches.

Given Data / Assumptions:

• “Budding” indicates a daughter cell forms as an outgrowth from the mother cell, often with polar growth.
• Hyphomicrobium species are classic budding and prosthecate bacteria.
• Purple non-sulfur phototrophs (e.g., Rhodopseudomonas/Rhodomicrobium) include budding representatives.

Concept / Approach:
Hyphomicrobium vulgare produces a hyphal stalk (prostheca) and buds off daughter cells from the hyphal tip. Several phototrophic alphaproteobacteria, historically grouped under Rhodopseudomonas or closely related genera, show budding or asymmetric reproduction. In contrast, Bacillus subtilis divides symmetrically by binary fission and can form endospores under stress rather than budding.

Step-by-Step Solution:

Verification / Alternative check:
Microscopy images show polar growth and daughter-cell release in Hyphomicrobium; culture morphology differs markedly from rod-shaped binary fission in Bacillus.

Why Other Options Are Wrong:

• Single selections (a) or (b) omit the other valid budding example.
• B. subtilis: not a budding organism.

Common Pitfalls:
Confusing stalked budding bacteria with those that form spores or prosthecae without budding; morphology and life cycle must be distinguished carefully.

Final Answer:
Both (a) and (b)