Biology Lyme and Phenylketonuria Disease

The prevalence of arthritis in the United States is 1 in 100,000 children. However, 1 in 10 children in Lyme, Connecticut, developed arthritis between June and September 1973. Allen Steere, a rheumatologist at Yale University, investigated the cases in Lyme and found that 25% of the patients remembered having a skin rash during their arthritic episode and that the disease was treatable with penicillin. Steere concluded that this was a new infectious disease and did not have an environmental, genetic, or immunologic cause.

What was the factor that caused Steere to reach his conclusion?
What is the disease?
Why was the disease more prevalent between June and September?
Part B: Newborn babies are tested for phenylketonuria (PKU), an inherited disease. Individuals with this disease are missing an enzyme to convert phenylalanine (Phe) to tyrosine; the resulting accumulation of Phe can cause mental retardation, brain damage, and seizures. The Guthrie test for PKU involves culturing Bacillus subtilis, which requires Phe to grow. The bacteria are grown on media with a drop of the baby’s blood.

What type of chemical is phenylalanine?
What does “no growth” in the Guthrie test mean?
Why must individuals with PKU avoid the sweetener aspartame?