Young tumors are soft and therefore vulnerable to secondary invasion by insects and saprophytic microorganisms. Adhesins are expressed by both pathogenic bacteria and saprophytic bacteria. Also included in this family are dematophytes and saprophytic species. Necrotrophic mycoparasites could only rely on saprophytic growth. Necrotrophic mycoparasites rely on decayed matter (saprophytic growth). It is easy to generate ammonium from organic fertilizer by saprophytic microorganisms. These spores may then infect tissue or remain in a saprophytic stage. "Stereum ostrea" is saprophytic in nature. Rhizopus is a genus of common saprophytic fungi on plants and specialized parasites on animals. Most Euglenozoa are photoautotrophic, but some are chemoorganotrophs (saprophytic). Biological production of ergot alkaloids is also carried out by saprophytic cultivations. Gastrodia elata is a saprophytic perennial herb in the family Orchidaceae. This plant prefers leaf litter in woodland areas and is saprophytic. Melioidosis is caused by gram-negative, motile, saprophytic bacteria named "Burkholderia pseudomallei". A few species are saprophytic and lignicolous, like those in the genus "Buchwaldoboletus".