E. coli--part of the normal flora of the human gut. Certain strains of E. coli produce various toxins that cause illness

Streptococcus pneumoniae, or pneumococcus

Helicobacter pylori. Coloured transmission electron micrograph (TEM) of a Helicobacter pylori bacterium (formerly known as Campylobacter pyloridis). Colonies of H.pylori occur on the stomach mucous membrane in people suffering gastritis, and this bacteria has been linked to stomach ulcer formation.

The human fungal pathogen Candida albicans alkalinizes the local extracellular environment.

Colorized low-temperature electron micrograph of a cluster of E. coli bacteria. Individual bacteria in this photo are oblong and coloured brown. As an alternative to using antibiotics for fighting E. coli infections in newborn and weaned pigs, scientists are finding promising results from introducing mixes of beneficial bacteria, obtained from other pigs, into the gut of young pigs.

Art of Diatom algae (from Ernst Haeckel) B305/0177 Rights Managed Credit: MEHAU KULYK/SCIENCE PHOTO LIBRARY

embryo by tiny palpitation, via Flickr

human intestinal flora

Escherichia Coli (E.Coli).

Moss spore capsule (Tortula muralis var. muralis) SEM

Mind Blown: Real Image of T4 bacteriophage (a virus) via electron microscope.

Escherichia coli

Most detailed model to date of Human Immunodeficiency Virus (HIV)

The Speed of Light

95-Million year old fauna and flora found in Ethiopian amber

Differentiating neuronal cells (actin, microtubules and DNA) (1000x)

human spinal nerve

This is a scanning electron microscope image from normal circulating human blood.