You do a gram stain of an unknown bacterium and the teacher guarantees you that is it a member of family enterobacteriaceae. however, your cells come out purple. what other clue might indicate that you do have a member of that family of bacteria?
a. tiny cocci bacilli in chains
b. tiny bacilli
c. rod-shaped cells with endospores
d. curved rods.

The correct answer is c.  rod-shaped cells with endospores

Explanation:

Most members of family Enterobacteriaceae can appear pink after gram staining due to porous membrane like Zymophilus, Pectinatus etc. Most of them form endospores which is a very tough outer covering formed by cells to resist the adverse condition. Many members of these family resides in intestine of animals and helps in food digestion.

These bacteria comes under phylum Firmicutes and mostly are rod shaped(bacillus). So when most of cells comes out purple the rod shaped cells with endospores indicates that gram stain contains the member of family Enterobacteriaceae.

correct answer is a. and d.