A research scientist working for a pharmaceutical company discovers a plant toxin that is capable of blocking ribosome function. However, only the function of ribosomes bound to the endoplasmic reticulum (ER) is affected. Would this toxin be able to negatively affect bacteria?

Yes, definitely.Both Ribosomes  either of the ER, and those  free  in the cells perform the same function of protein synthesis. So  the toxin will affect bacteria process of protein synthesis negatively.

Explanation:

The major function of Ribosomes is to mediate the process of translation during protein synthesis. Ribosomes  through its  large and small units ensures that complementary codons and anticodons from the tRNA and mRNA are paired for correct sequence amino acids needed in polypeptides chains of protein. Thus they convert genetic code, transcribed to mRNA to, amino acid sequence  in protein.

Therefore, with the toxins blockade of the ribosomes functions,protein synthesis of bacteria is therefore blocked. Thus needed enzymes and hormones  for metabolic activities of  bacteria are blocked, and therefore the bacteria cells will be negatively affected.