bacteroid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various bacteria, especially those of the genus Rhizobium, that carry out nitrogen fixation in the root nodules of leguminous plants and often change markedly in size and shape after they enter the roots.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Biol.) Resembling bacteria.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun dated A micro-organism such as a bacterium or yeast.
• noun A bacterium of the species Bacteroides.
• noun A symbiotic form of the nitrogen-fixing bacterium Rhizobia, or the root nodule that it produces.
• adjective biology Resembling bacteria.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective resembling bacteria
• noun a rodlike bacterium (especially any of the rod-shaped or branched bacteria in the root nodules of nitrogen-fixing plants)