Crazy Shapes in Two Lava Tubes

Crazy Shapes in Two Lava Tubes

The central question of this album is what to make of all the strange bacterial shapes we are finding in lava tubes. In high school and college microbiology classes, we learn that the basic or common bacteria shapes include coccid (round), rod, spirillum (rod with a twist), spirochete, vibrio and filamentous. Scientists have also found bacteria that are shaped like stars, squares, corkscrews and helices. Some of the microorganisms in this album show these basic shapes, while others do not.

The cell wall or cytoplasmic membrane is the usual outer layer of a bacteria cell but additional membranes and appendages can appear on the bacteria cell surface. The cytoplasmic membrane is made of a phospholipids bilayer and can have membrane proteins that bridge across it. These proteins can protrude past the cytoplasmic membrane, providing additional shape and texture to the cell wall. Some bacteria can produce or secrete capsules (a tight polysaccharide layer around the bacteria that excludes most smaller particles) and slime layers (a looser polysaccharide or protein layer that does not exclude particles). These layers can serve as a method of attachment, create biofilms, and protect the cell from host defenses or desiccation. Many bacteria also produce fimbriae and pili, which are protein filaments on the surface of the cell that help with attachment, exchange of genetic material, motility or environment sensing around them. Some bacteria also have flagella, which are longer than fimbriae and pili and mainly are used for motility. These bacteria can have one or many flagella at one end (monotrichous or lophotrichous), at both ends (amphitrichous), or all over the cell (peritrichous). Finally bacteria can produce budding appendages, tubes, stalks, hypha and nanowires on their cells surface.

Given all the different shapes and appendages that bacteria can have, it is not surprising that we are finding some pretty amazingly shaped microbes in our SEM images. However, what are the different shapes and appendages that we are seeing? Can we even determine what we are looking at on the bacteria cell? We are confident that these are images of microorganisms, given the high carbon peaks reported by EDS analysis (for more information about this, please see the “What is EDS/EDX” album in the IDEC Image Gallery). But we hope some addition eyes will help us get a better understanding of what kinds of shapes of bacteria we are seeing and, more importantly, how are these shapes being created.