organic acid which gives vinegar its sour taste and pungent smell. Produced by acetic acid bacteria including Clostridium acetobutylicum and Acetobacter, found universally in food, water and soil, produced in food spoilage and in the human body - for example, in vaginal lubrication.  This  second simplest carboxylic acid (after formic acid) is an important chemical reagent and industrial chemical, mainly used in the production of cellulose acetate for photographic film and polyvinyl acetate for wood glue, as well as synthetic fibers and fabrics. the acid that gives vinegar its characteristic taste. 
One of short chain fatty acids (SCFAs, also called volatile fatty acids) containing fewer than 6 carbons: Formic acid (C1), acetic acid (C2), propionic acid (C3), butyric acid (C4), and valeric acid (C5). The gut microbial metabolites SCFAs profoundly regulate T cell differentiation in the body, boosting immune system.

if raised, suggests bacterial fermentation due to excess carbohydrate reaching the colon; levels are not significantly altered in patients with malignancy or diabetes mellitus, but severe liver disease and severe acidosis were both associated with increased acetate concentrations. Elevated blood acetate is also an indicator of fast ethanol elimination in chronic alcoholics.

Acetobacter is bacteria converting alcohol to acetic acid and oxidizing lactate and acetate into carbon dioxide and water. 
It is used in the commercial production of vinegar, as fermentation starter cultures, and is found in gut microbiomes of some living organisms. 

Acetobacter aceti bacteria are a widespread group of gram-negative, obligate aerobic rods which oxidize ethanol (alcohol) into ethanoic (acetic) acid. They occur mainly in sugary, acidic and/or alcoholic surroundings and play a positive, neutral, or detrimental roles in food and beverages. It can be found in mangoes, bananas, sugar cane, sweet potato, coffee, cameroon grass, ragi, tea, pineapple, and mealy bugs. 

simplest aromatic ketone, in small amounts can be found in apple, apricots, cheese, chicory, banana, beef, and cauliflower. It is a precursor to useful resins and fragrances, is used in chewing gum and is an  ingredient in fragrances that resemble smell of almond, cherry, honeysuckle, jasmine, and strawberry. 
In humans, acetophenone is metabolized to benzoic acid, carbonic acid, and acetone, but it can be also excreted in its original form in feces and saliva.
Deuterated acetophenone smells fruitier than ordinary acetophenone. It also smells slightly of bitter almonds, just like many compounds containing the cyanide or nitrile group (C≡N) - as both C–D and C≡N bonds vibrate at the same frequency (about 2200 cm-1).   See also 2-aminoacetophenone

a derivative of testosterone also known as androsta-4,16,-dien-3-one, this endogenous steroid has been described as having potent pheromone-like activities in humans. This chemical component of male sweat (and semen) can influence not only women (improving mood, inducing ovulation) but also other men's behavior making them more cooperative. Androstadienone's odor can be described as vaguely musky, but it depends on the gene OR7D4 if it smells pleasant or repulsive.  

Several hundred mold species found in various climates worldwide. Belongs to Ascomycota (sac fungi) group. Common contaminants of starchy foods (such as bread and potatoes), and grow in or on many plants and trees. Aspergillus niger can be found growing on damp walls, as a major component of mildew. Aspergillus oryzae can be found in Japanese sake where it is used to break down the starches (rice, manioc) into simpler sugars. Some Aspergillus species are pathogenic. Aspergillus flavus produces aflatoxin which is both a toxin and a carcinogen, and which can contaminate foods such as nuts. The most common causing allergic disease are Aspergillus fumigatus and Aspergillus clavatus.

Bacteroidetes bacteria that is part of the normal flora of the human colon but can cause infection if it gets into bloodstream during surgery, disease, or trauma.
Bacteroides fragilis may prevent intestinal inflammatory disease as this 
bacteria produces Polysaccharide A (PSA), which suppresses the inflammatory response of the immune system (by suppressing IL-17 production). The combination of Bacteroides fragilis ATCC 25285, Clostridium difficile ATCC 700057 and Fusobacterium necrophorum ATCC 25286 produce odor associated with flatulence. 

Bacteroidetes is a diverse group of bacteria common in human gut, in marine and freshwater systems. Their levels rise as body weight is decreased. The name of this bacterial phylum changed several times over the past years and is also known as the Cytophaga–Flexibacter–Bacteroides (CFB) group. It includes four classes: Bacteroidia (858 strains), Flavobacteria (3583 strains), Sphingobacteria (787 strains), and Cytophagia (765 strains), and many unclassified strains representing around 7000 different species (NCBI, October 2010). They are non-motile, flagellated, or move by gliding.

Bacteroidetes in the gut are responsible for degradation of high molecular weight organic matter, i.e., proteins and carbohydrates. Their genomes appear to be highly plastic and frequently reorganized through genetic rearrangements, helping them to adaptation to distinct ecological niches.

hydrocarbon present in coal tar and petroleum, cigarette smoke, used in chemical synthesis, motor fuels, solvents, detergents, pesticides, personal care items such as nail polish or hair color and many other substances. It has a sweet, aromatic, gasoline-like odor. Benzene is a carcinogen that causes leukemia as well as a number of other illnesses. Virtually the entire U.S. population is exposed to benzene, at least in small amounts -- at gas stations (it's in the gasoline), in diesel exhaust or from cigarette smoke, including second-hand smoke. Benzene is also a problem in a number of workplaces, including oil refineries, coal-coking operations at steel mills, chemical processing plants, rubber manufacturing plants and laboratories, where it is often used as a solvent for other chemicals. You can avoid one significant source of benzene by stepping away from the gas pump when refueling your car.

Benzene levels in breath increase after exposure to tobacco smoke, but there are additional sources of benzene in breath than ambient air. It is difficult to establish exact relationships with the number of cigarettes smoked, or with other benzene exposures such as diet.