Fungi are the organisms that have long thread-like structures called hypha in their body. Many hyphae together form a mass called mycelium. Fungi are eukaryotes and have a well-defined nucleus in their cells. They also have cell walls that are made up of chitin. Fungi are mostly multicellular. However, yeast is the fungi that have a single cell in their body. Fungi are heterotrophs and derive their nutrition by parasitic or saprophytic mode of nutrition. Therefore, the given description tells that the microbe should be a fungus.
In order for gas to leave a planet it needs to be hot enough and to overcome the planets gravity. The outer planets are colder and are very big compared to earth.