Ear
Description of Niche
The Human Ear: The human ear is comprised of 3 main parts: outer, middle, and inner. The outer ear consists of the pinna, which is the visible part of the ear, and the auditory ear canal to the tympanic membrane(ear drum). The membrane separates the outer ear from the middle ear which is an air-filled space that is connected to the nasopharynx via the eustachian tube. The middle ear consists of the malleus, incus, and stapes. These three tiny bones carry sound from the ear drum to the inner ear. The inner ear (aka the bony labyrinth) is comprised of the cochlea and the vestibular apparatus.(1)
Physical Conditions?
The conditions of the pinna are similar to that of the skin(for more information please refer to the skin page). Closer to the ear canal the skin develops a thin lining of ear wax. Ear wax is composed mostly of dead skin cells and keratin with a small mixture of cerumen, sweat, and oil. Cerumen is secreted from the ceruminous glands located in the first third outer part of the ear canal and is thought to be composed mainly of cholesterol, squalene, wax esters, ceramides, and triglycerides. The cerumen also has antibacterial/fungal properties which can be attributed to its slight acidic pH of 6.1 and the presence of lysozyme. In normal individuals, the ear wax is continuously pushed out of the ear canal by the slow migration of the top layer of skin cells from the tympanic membrane towards the outer ear. The ear wax traps any foreign particles/organisms on its way out. The ear canal is a dark, moist, close to body temperature(~37C), and abundant with nutrients from dead skin cells.(2)(3) If not for the cerumen, the ear canal would be a very hospital place for microbes.
The middle ear
The inner ear consists of two fluid-filled membraneous structures, the cochlea and the vestibular apparatus, surrounded by a hard bony shell. The two structures are adjacent to each other and share the fluid.
Conditions under which the environment changes
Do any of the physical conditions change? Are there chemicals, other organisms, nutrients, etc. that might change the community of your niche.
In regards to the ear, the environment of the outer ear is subject to the most variation. The one of the biggest effects on the environment of the ear would be those that remove the ear wax. This can occur through excessive showering or swimming as water/soap can wash away the thin protective lining of ear wax. Loss of the cerumen encourages the growth of microbes that are normally kept under control by its antimicrobial properties. Use of cotton swaps or hair pins is also common practice as a means to remove ear wax. In addition to the removal of the ear wax, they can also scratch the surface of the skin which can allow microbes to get in to the unprotected tissue. Use of cotton swabs also can push the ear wax further into the canal, which if allowed to build up can become impacted and damage the inner ear canal and the tympanic membrane. These too provide opportunities for microbes to infect the underlying tissue. Infections in the outer ear or damage to the tympanic membrane also provide venues for microbes to invade the middle and inner ear.
Who lives there?
Which microbes are present?
You may refer to organisms by genus or by genus and species, depending upon how detailed the your information might be. If there is already a microbewiki page describing that organism, make a link to it.
Do the microbes that are present interact with each other?
Describe any negative (competition) or positive (symbiosis) behavior
Do the microbes change their environment?
Do they alter pH, attach to surfaces, secrete anything, etc. etc.
Do the microbes carry out any metabolism that affects their environment?
Do they ferment sugars to produce acid, break down large molecules, fix nitrogen, etc. etc.
Resources
1)
2)
3)Bortz JT, Wertz PW, Downing DT. "Composition of cerumen lipids." J Am Acad Dermatol. 1990 Nov;23(5 Pt 1):845-9.
http://www.meddean.luc.edu/depts/otolaryn/patient_ed/pdf/ENT%20INNER%20EAR%20FLUID%20IMBALANCE.pdf
http://jama.ama-assn.org/cgi/content/abstract/291/8/981 ( Outbreak of Pseudomonas aeruginosa Infections Caused by Piercing of Upper Ear Cartilage)
