After gaining his university-entrance qualification (Abitur), he embarked on a degree in biology at Darmstadt University of Technology in 1968, graduating from the Institute of Microbiology in 1973.

In 1986, Gruss was appointed a scientific member and director of the Department of Molecular Cell Biology at the Max Planck Institute for Biophysical Chemistry in Göttingen.

A study of the pancreas which he conducted enabled him to detect genes involved in the development of insulin-producing islets of Langerhans.

[9] Upon taking office, Gruss was regarded by the press as an "American-style man of action" and an "unassuming high flyer".

He also spoke out in favour of a reliable financial framework: "Only adequate rates of increase – predefined for a lengthy period of time – for the budget of the MPS can guarantee planning security".

[18] The Lead Discovery Center was founded as a new subsidiary in Dortmund in 2008 to improve the technology transfer of newly developed pharmaceutical drugs.

[21] In an interview published by Spiegel Online, Gruss outlined a new strategy for establishing "Max Planck Centers" for cooperating with foreign research institutions; some of these are already in place in cities like Shanghai, Buenos Aires and New Delhi.

[22] Gruss championed the cause of transferring his findings into practical application: he co-funded the biopharmaceutical company DeveloGen AG in Göttingen (now part of Evotec) in 1997, together with fellow developmental biologists Herbert Jaeckle [de] (Max Planck Society), Wolfgang Driever (University of Freiburg) and the entrepreneur Herbert Stadler.

The company concentrated on developing new treatments for metabolic and endocrinological diseases with a special focus on diabetes.