Graduate Studies


Microbiology recognizes that microbial inventions have profoundly shaped every aspect of the biosphere and geosphere throughout Earth history. Many important molecular and cellular processes in eukaryotes are now known to have first arisen in bacteria and archaea, and microbial metabolic activities control numerous geochemical cycles. Microorganisms have served and will continue to serve as model systems in many areas of science, ranging from basic biology and biochemistry, to the understanding of physical principles governing biological systems, to emerging questions of robustness, stability, and design in complex networks. Interactions among microbes within communities, as well as interactions between microbial communities and their environments, are poorly understood. Yet studying these interactions is key to understanding fundamental relationships in nature, such as: 1.) the feedback loops connecting microbial activities in aquatic or terrestrial habitats with changes in composition of the atmosphere, hydrosphere and geosphere, and 2.) the symbiotic associations that sustain diverse forms of life today. For example, the interactions between a mammalian host and its microbiota are essential to the host's normal functioning and development, not merely the cause of infectious disease. Due to their metabolic versatility, microorganisms are likely to emerge as key engineering components for solving global societal problems, ranging from human health, to energy, to providing clean water to more than one billion people who currently live without it.

Caltech's version of microbiology is unique. Over fifteen faculty from four divisions (BBE, CCE, GPS, EAS) work together to train students in how to understand microbial systems at various spatial and temporal scales: from the molecular to the global, from the present to the past. This interdisciplinary training involves study of molecular and cellular biology, physiology, chemistry, ecology, and quantitative reasoning.

Sample Courses

  • Bi 165. Microbiology Research: Practice and Proposal
  • ESE/Bi 166. Microbial Physiology
  • ESE/Bi 168. Microbial Metabolic Diversity
  • GE/ESE 178. Microbial Ecology

For more information, visit the Caltech Microbiology website.

Application for the Biology PhD Option and any of the tracks is through the Caltech Graduate Studies Office.