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What sturdy fibers are more biodegradable than plastic bristles?
Assume the baccteria which eat the toothbrush bristles are a 95% or greater match in DNA comparison to baccteria which pre-date the year 2000.
Please, do not consider baccteria which were bred for ourposes of eating plastic.
Also, assume that the tooth brush is kept inside of a cleaning solution such as 99% pure alchohol.