Those who do require oxygen to live are considered aerobes. The bacteria who don't use oxygen to live are known as anaerobes. The shape of specific bacteria provides for the next step in the identification process. Hans Christian Joachim Gram, a Danish microbiologist, developed a method for distinguishing bacteria by their different reaction to a stain. However, in bacteria the DNA is arranged in a circular fashion rather than in strands.
Bacteria also contain ribosomes which, like in eukaryotic cells, provide for protein synthesis.
In order for a bacterium to attach itself to a surface, it requires the aid of pili, or hairlike growths. Bacteria, just like sperm cells, have flagella which assist in movement. But, sperm cells only have one flagellum, whereas bacteria contain flagella at several locations throughout their body surface. Although most bacteria are not harmful, a small fraction of them are responsible for many diseases. These bacterial pathogens have affected humans throughout history.