I remember reading this in the 1980s, it may have been published much earlier. A space probe penetrates the clouds of Venus, but returns with an infectious fungus-like organism which proliferates wildly. It's thought that there must be other organisms which feed on this one, so a team of astronauts are sent to determine what these are and bring one back as a control. While doing so, they become infected with the fungus. They discover a possible control organism and in desperation, expose themselves to it which cures them, leading to a successful mission.
There was a series of books with the same lead character. In one of these, it was discovered that the moon had become destabilised and would crash into the Earth. A retired scientist built an anti-gravity device, but was at first reluctant. He was persuaded because he did not want his cat to perish. In another, a lone astronaut travels further out into the solar system than anyone previously and hears "voices" on his radio which cause him to go mad. The same "voices" save the lead character when he and his companions are possessed by the spirits of extinct Martians, who are vulnerable to them.