**2. Importance of drug discovery**

The importance of look for new bioactive compounds to synthesize new drugs it's based by a main objective of saving human life that it's lose by illness. Also, it is important to recog‐ nized that the drug discovery projects, help those countries that target their efforts in this area to economically and sociality develop themselves, because when chemical compounds

are discovered from microorganism that lives in natural environments, this chemical can be exploited industrially and generate more jobs.

ing public health problem. Some examples of diseases that have become very hard to treat with the current drugs are wound infections, septicemia, tuberculosis, pneumonia, and gon‐ orrhea, to name a few. One part of the problem is that bacteria and other microbes that cause infections are remarkably adaptable and have developed several mechanisms to be

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Also, it`s been reported that over-prescription and the improper use of antibiotics has led to the generation of antibiotic resistance bacteria that use to be susceptible at those antibiotics [5].

**a. Avoiding entrance of antibiotic into the bacteria cell:** Bacteria and other microbes can actually change the properties of its membrane by changing its grade of permeability by reducing the number of ion channels which are the entrance of some drugs to diffuse into the cells. Another way to get rid of antibiotics in some bacteria is use adenosine tri‐ phosphate (ATP) to obtain energy to activate this ion channels and pump it out of the

**b. Editing transmembrane protein expression**: The mechanism of several antibiotics it`s to interact specifically with molecules in the membrane of the microbes and preventing it from interacting with other molecules (usually proteins) inside the cell. Some bacteria respond by changing the chemical structure or the expression of the molecule (replac‐ ing it with another molecule) so that the antibiotic can no longer recognize it or bind to

**c. Bacterial enzymes that destroy antibiotics:** Some bacteria can be resistant to antibiotics by neutralizing them directly. For example, some organisms may obtain new genes that encode proteins like enzymes that neutralize antibiotics agents before they get to their targets. An example of this enzymes can be found in the β–lactamases like penicillinas‐ es, cephalosporinases, carbenicillinase, cloxacilanase, carbapenamase, metalloenzyme that destroy the β-lactamics (penicillins, monobactams, carbapenems, and cephalospor‐ ins). The β–lactamases can be isolated from Gram Negative Bacteria: *Escherichia coli, En‐ terobacter cloacae, Citrobacter freundii, Serrati amarcescens*, and *Pseudomona aeruginosa.* The mechanism of action of β–lactamases is the breaking of β-lactam ring of the antibiotic, thus destroying the drug [6]. Other example of this is *Pseudomona sp.* erithromycinester‐ ases that degrade erythromycin by hydrolysis of the lactone ring of erithromycin [7].

Cancer is an illness that comprises more than hundred types. This disease appears when old cells are not replaced by new cells and are accumulated in a mass of tissue known as tumor" [4]. To cite some statistics data; cancer is responsible for one of every four deaths in the United States.

immune to antibiotics and other antimicrobial drugs.

cells.

it.

**5. Cancer**

**4. Mechanisms of bacteria to become antibiotics resistant**

Now, the new drugs and innovative procedures are usually able to keep people alive for a long time with better conditions that would have previously been rapidly fatal, such as can‐ cer and end-stage heart, liver, lung, kidney, and neurologic diseases. As a result, most peo‐ ple in modern countries die from long-term chronic conditions that are characterized by a prolonged period of distressing symptoms and progressive loss of function.

According with World Health Organization (WHO) of "*57 million global deaths in the last re‐ port in 2008, 36 million (63%), were due to no communicable diseases (NCDs). The four main NCDs reported are cardiovascular diseases, cancers, diabetes and chronic lung diseases. The burden of these diseases is rising disproportionately among lower income countries and populations. In 2008, nearly 80% of no communicable disease deaths -- 29 million -- occurred in low- and middleincome countries with about 29% of deaths occurring before the age of 60 in these countries. The leading causes of NCD deaths in 2008 were cardiovascular diseases (17 million deaths, or 48% of all NCD deaths), cancers (7.6 million, or 21% of all NCD deaths), and respiratory diseases, including asthma and chronic obstructive pulmonary disease (4.2 million). Diabetes caused another 1.3 mil‐ lion deaths*" [3]. As we can see, in the WHO's statistic data, there are less number of people that die with microbial infection, it can be said to thanks to the constant development of pharmaceutical drugs.

The discovery of new bioactive compounds from microorganism present in the ambient, needs the previously determination of diversity, because by knowing the kind of microbes that live in a certain site, we can be able to design strategies and culture methods adapted for the different types of microorganism present in nature [4]. We can be able to screen chemical bioactivity only if we can culture the microorganism, because we need the microbi‐ al biomass to obtain the compounds. To culture microorganism from natural sources is not an easy topics, because, when we try to cultivate bacteria or fungi from substrates and con‐ ditions that are in constant change, and incubate them in a static temperature and nutrients; many microbes don't resist this transformation of circumstances and die.
