Brevundimonas species is considered an opportunistic human pathogen that can cause multiple types of invasive and severe infections in patients with underlying pathologies. Treatment of these pathogens has become a major challenge because many isolates are resistant to most antibiotics used in clinical practice.

Nanoparticles (NPs) have gained great attention in recent years due to their extensive and innovative applications in the field of medicine. However, conventional physicochemical approaches for the synthesis of NPs may be limited and costly, and the reaction by-products are potentially toxic for human health and the environment. Bio-mediated synthesis of NPs exploiting microorganisms as nanofactories has emerged as an alternative to traditional methods, as it provides economic and environmental benefits. Tropical ecosystems harbor a high diversity of endophytes, which have a diverse array of metabolic pathways that confer habitat adaptation and survival and that can be used to produce novel bioactive compounds with a variety of biological properties. Endophytic bacteria and fungi cultivated under optimum conditions have potential for use in biogenic synthesis of NPs with different characteristics and desired activities for medical applications, such as antimicrobial, antitumoral, antioxidant and anti-inflammatory properties. The bio-mediated synthesis of metal-based NPs can be favored because endophytic microorganisms may tolerate and/or adsorb metals and produce enzymes used as reducing agents. To our knowledge, this is the first review that brings together exclusively current research highlighting on the potential of endophytic bacteria and fungi isolated from native plants or adapted to tropical ecosystems and tropical macroalgae as nanofactories for the synthesis of NPs of silver, gold, copper, iron, zinc and other most studied metals, in addition to showing their potential use in human health.

The growing antimicrobial resistance and persistence of pathogenic microorganisms in infections–particularly in nosocomial infections–have become a major problem for public health worldwide. One of the main causes of these issues is the formation of biofilms, which are microbial communities associated with extracellular polymeric substances (EPS) that form a slimy extracellular matrix, causing the bacteria to become more tolerant to usual drugs in these structures. Thus, the search for new antibiofilm compounds is part of a strategy to deal with this problem. Endophytic microorganisms such as bacteria and fungi, mutualistically associated with plants, are sources of compounds with biological properties, including antimicrobials, and can be important allies in the synthesis of antibiofilm. These secondary metabolites can interfere with cell-to-cell communication and cell adhesion ability, promoting the dispersal of bacterial colonies and affecting biofilm. Since endophytes are cultivable in laboratory conditions, these microorganisms are environmentally friendly, as they do not contribute to pollution, are easy to handle and are produced on a large scale. Furthermore, metabolites from endophytes are of natural origin and may contribute to the reduced use of synthetic drugs. Considering these aspects, this chapter will focus on the characterization of endophytic microorganisms as potential active sources of antibiofilm and antimicrobial compounds with applications in medicine.