Concept:
Antibiotics are chemical substances produced by microorganisms that inhibit or kill other microorganisms.
Step 1: Identify the organism related to antibiotics.
The famous antibiotic penicillin was obtained from the fungus Penicillium.
\[
\text{Penicillium} \rightarrow \text{Penicillin}
\]
Step 2: Check other options.
Streptococcus is a bacterium.
Rhizobium is a nitrogen-fixing bacterium.
Puccinia is a fungus, but it is mainly known as rust fungus, not as a source of common antibiotic.
Step 3: Final answer.
Therefore, the correct source of antibiotics among the given options is:
\[
\text{Penicillium}
\]
\[
\therefore \text{Correct Answer is (B)}
\]