**3. Conclusions**

More than two centuries of work to isolate actinobacteria from natural resources have ended in major discoveries, academic contributions, and important recognitions. Novel actinobacteria represent the entree of new natural compounds of significant importance. For more than 15 years our research group has developed and applied selective isolation strategies exploring distinct natural unexplored sites or less studied ecological niches in Mexico. To avoid the isolation of the "same bugs," it is needed to use different selective isolation strategies, pre-treatments of the environmental sample, supplementation of the media with a specific concentration of antibiotics and antifungal compounds while carefully selecting the target organisms.

The results presented in this chapter support the proposal that the isolation of microorganisms is not "*an old fashioned and boring work*"; it requires creativity, experience, knowledge, and patience. Moreover, to study physiology or genetic potential of a specific microorganism indeed needs to be cultivated in the laboratory.

Actinobacteria is one most of the diverse and complex groups of bacteria and produces more than 80% of the antibiotics used in medicine today. Their ability to produce novel natural compounds, such as antibiotics and novel cancer compounds is widely recognized. According to the World Health Organization (WHO) there is an urgent need to discover novel antibiotics for priority pathogenic bacteria and emerging pathogenic organisms [43] and the first step to respond and to contribute with this global initiative is to isolate novel actinobacteria. To our knowledge, our reports here are one of the few research projects in our country that are dedicated to study the ecological role and the genetic potential of novel actinobacteria from unexplored sites or less studied ecological niches in Mexico.

### **Acknowledgements**

Our research was supported by Instituto Politécnico Nacional (IPN)—Secretaría de Investigación y Posgrado (SIP), Grants SIP 20170432, 20170434, 20170410, 20181167, 20181528, 20181803, 20196605, 20196630, 20196649, 20201026, 20201893, 20202083, 20210987, 20211209, and 20211740. L.C.-C. was supported by a Ph.D. Scholarship from Consejo Nacional de Ciencia y Tecnología (CONACyT, Mexico) no. 270230 and Beca de Estímulo Institucional de Formación de Investigadores Program (BEIFI-IPN). ETQ, CJHG and JCCD acknowledge Comisión de Operación y Fomento de Actividades Académicas del Instituto Politécnico Nacional (COFAA), Estímulo al Desempeño de los Investigadores (EDI) and Sistema Nacional de Investigadores (SNI-CONACYT) fellowships. A.A-V ackcnowledges a Mexican Postdoctoral Scholarship Program 3 and 4, Program 4, 2020–2021 and Program 1 and 2, Program 2, 2021–2022 (CONACyT, Mexico).
