In Tennessee is it legal for an employer to automatically deduct the wages of an hourly employee for a lunch break that was not taken.

Under Tennessee law, a private employer must provide each employee with a 30 minute rest/meal break when the employee is scheduled to work more than 6 hours except in environments were employees have "ample opportunity to rest or take an appropriate break."  The break is unpaid.  Your employer is apparently deducting the unpaid break time from your check, as they are entitled to do under the law.  If your employer requires you to work for the 6 hour period without a 30 minute break, then they are required to pay for the time worked, and may also be in violation of the law, but that depends on whether your work environment provides opportunities for rest or breaks without the 30 minute mandatory break and the other circumstances of your employment.