( ( ( ( A ( ( potentially fatal ) condition ) ) , ) ( Lyme disease ) ) ( ( is ( caused ( by ( ( a bacterium ) ( ( transmitted ( to humans ) ) ( through ( ( the bite ) ( of ( a ( black-legged tick ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (ADJP (RB potentially) (JJ fatal)) (NN condition)) (, ,) (NP (JJ Lyme) (NN disease))) (VP (VBZ is) (VP (VBN caused) (PP (IN by) (NP (NP (DT a) (NN bacterium)) (VP (VBN transmitted) (PP (TO to) (NP (NNS humans))) (PP (IN through) (NP (NP (DT the) (NN bite)) (PP (IN of) (NP (DT a) (JJ black-legged) (NN tick)))))))))) (. .)))
A potentially fatal condition, Lyme disease is caused by a bacterium transmitted to humans through the bite of a black-legged tick.
(ROOT (S (NP (JJ Lyme) (NN disease)) (VP (VBZ is) (VP (VBN caused) (PP (IN by) (NP (NNS bacteria))))) (. .)))
Lyme disease is caused by bacteria.