**6. Natural source for drug discovery**

### **6.1. Drug discovery from air microorganisms**

The atmosphere its well characterized for possess a good light intensity, extreme tempera‐ ture variations, low concentration of organic matter and water, hence become a very hostile place for microorganism. However, there are a numerous quantity of microbes founded in the atmosphere, most of them introduced by human activity.

Bioaerosols are airborne particles that are biological in foundation. Bioaerosols can be formed from nearly any process that involves biological materials and generates enough en‐ ergy to separate small particles from the larger substance, such as wind, water, air, or me‐ chanical movement. Plants, soil, water, and animals (including humans) all serve as sources of bioaerosols and are present in most places where any of these sources live.

It's second only after heart disease as a cause of death in this country. About 1.2 million Ameri‐ cans were diagnosed with cancer in 1998. Of that number, more than 500,000 are expected to die of this disease. Cancer can attack anyone, but the chances of getting the disease increase with age. The most common forms of cancer are skin, lung, colon, breast and prostate cancer. Cancer is a disorder that affects the genes. There were an estimated 12.7 million cancer cases around the world in 2008, of these 6.6 million cases were in men and 6.0 million in women. This number is ex‐ pected to increase to 21 million by 2030. Lung cancer is the most common cancer worldwide con‐ tributing nearly 13% of the total number of new cases diagnosed in 2008. Breast cancer (women only) is the second most common cancer with nearly 1.4 million new cases in 2008 and colorectal cancer (Figure 1) is the third most common cancer with over 1.2 million new cases in 2008 [8].

**Figure 1.** Cancer Colorectal HCT-116 cell culture in McCoy medium at 40 X amplification

The atmosphere its well characterized for possess a good light intensity, extreme tempera‐ ture variations, low concentration of organic matter and water, hence become a very hostile place for microorganism. However, there are a numerous quantity of microbes founded in

Bioaerosols are airborne particles that are biological in foundation. Bioaerosols can be formed from nearly any process that involves biological materials and generates enough en‐ ergy to separate small particles from the larger substance, such as wind, water, air, or me‐

**6. Natural source for drug discovery**

312 Drug Discovery

**6.1. Drug discovery from air microorganisms**

the atmosphere, most of them introduced by human activity.

Microorganisms are frequently considered passive habitants of the air, dispersing via air‐ borne dust particles (Figure 2). However, latest studies suggest that many airborne microor‐ ganisms are metabolically active, even up to altitudes of 20,000 m. Also, it has been suggested, that some airborne microbes may modify atmospheric conditions [9].

**Figure 2.** Fungal strains from air samples in Valle de las Palmas, Mexico.

Several studies reported a great variety of microorganism present in air samples, for exam‐ ple, a study realized in Mexico, in 2007, showed 21 species of bacteria founded in air sam‐ ples from landfill, some of them are pathogenic and opportunistic bacteria, the most abundant are *Pasteurella haemolytica, Serratia plymuthica*, *Escherichia coli* y *Klebsiella pneumonia* and 19 fungal species, 7 of them allergenic, *Cladosporium herbarum, Aspergillus* sp y *Penicilli‐ um* sp. [10]. Despite this, *Serratia plymuthica*it's well known to possess 2-amino-3-(oxir‐ ane-2,3-dicarboxamido)-propanoyl-valine has been shown to inhibit the growth of the human pathogen *Candida albicans* efficiently [11].

Another studies found airborne microbes collected at indoor air with filters installed in two shopping centers in Singapore. The most common microorganism appears to be several spe‐ cies of *Brevundimonas* (50%) [12] other study has identified *Brevundimonas diminuta*as pro‐ ducer of a nematicidal metabolite known as (R)-(-)-2-ethykhexan-1-ol which have a strong activity against *C. elegans* and *B. xylophilus* [13].
