<em>Bordetella pertussis</em> b/w <em>Bordetella pertussis</em>

Bordetella pertussis

These bacteria cause the respiratory infection known as whooping cough. It mainly occurs in infants and is characterised by fits of coughing that end in loud inspiratory whoops.

Archaea

Archaea can be spherical, rod, spiral, lobed, rectangular or irregular in shape. An unusual flat, square-shaped species that lives in salty pools has also been discovered. Some exist as single cells, others form filaments or clusters. Until the 1970s this group of microbes was classified as bacteria.

Many archaea have been found living in extreme environments, for example at high pressures, salt concentrations or temperatures, and have been nicknamed extremophiles. Their cell wall differs in structure from that of bacteria and is thought to be more stable in extreme conditions, helping to explain why some archaea can live in many of the most hostile environments on Earth.

Examples of archaea habitats are boiling hot springs and geysers such as those found in Yellow Stone Park, USA and ice such as the Artic and Antarctic oceans which remain frozen for most of the year.