MicroBiology-Draft/Sample

Neisseriaare cocci that live on mucosal surfaces of the human body. They are fastidious, or difficult to culture, and
they require high levels of moisture, nutrient supplements, and carbon dioxide. Also,Neisseriaare microaerophilic,
meaning that they require low levels of oxygen. For optimal growth and for the purposes of identification,Neisseria
spp. are grown on chocolate agar (i.e., agar supplemented by partially hemolyzed red blood cells). Their characteristic
pattern of growth in culture is diplococcal: pairs of cells resembling coffee beans (Figure 4.6).

Figure 4.6 Neisseria meningitidisgrowing in colonies on a chocolate agar plate.

The pathogen responsible for pertussis (whooping cough) is also a member of Betaproteobacteria. The bacterium
Bordetella pertussis, from the order Burkholderiales, produces several toxins that paralyze the movement of cilia in
the human respiratory tract and directly damage cells of the respiratory tract, causing a severe cough.

Table 4.3summarizes the characteristics of important genera of Betaproteobacteria.

Class Betaproteobacteria

Example

Genus

Microscopic

Morphology

Unique Characteristics

Bordetella A small, gram-negative

coccobacillus

Aerobic, very fastidious;B. pertussiscauses pertussis (whooping

cough)

Burkholderia Gram-negative bacillus Aerobic, aquatic, cause diseases in horses and humans (especially

patients with cystic fibrosis); agents of nosocomial infections

Leptothrix Gram-negative,

sheathed, filamentous

bacillus

Aquatic; oxidize iron and manganese; can live in wastewater

treatment plants and clog pipes

Neisseria Gram-negative, coffee

bean-shaped coccus

forming pairs

Require moisture and high concentration of carbon dioxide; oxidase

positive, grow on chocolate agar; pathogenic species cause

gonorrhea and meningitis

Thiobacillus Gram-negative bacillus Thermophilic, acidophilic, strictly aerobic bacteria; oxidize iron and

sulfur

Table 4.3

1. What characteristic do all Betaproteobacteria share?

150 Chapter 4 | Prokaryotic Diversity

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