Biological and living lyotropics

Abstract The interface between lyotropic liquid crystals and biology is broad. Phospholipids, one of the structural components of the cellular membrane, are amphiphilic molecules. The formation of micelles in mixtures of amphiphilic molecules and water above the critical micellar concentration is an example of these super-molecular structures. This type of super-molecular structure is observed in the human lipoproteins, Low Density (LDL) and High Density (HDL) Lipoproteins. In this chapter we discuss the existence of lyotropic mesophases in systems where the basic units are viruses (tobacco mosaic virus and filamentous phage virus fd), DNA and RNA, actin filaments, and cellulose nanocrystals and derivatives. The term ‘living liquid crystals’ was proposed to designate a class of active matter composed by bacteria in a lyotropic water-based, non-toxic, liquid crystal. Interestingly, the individual and collective motions of the bacteria strongly couple with the short-range positional and long range orientational ordering of the lyotropic liquid crystal.