**1. Introduction**

Water, as an essential resource for the maintenance of life, must be ingested in significant amounts daily. However, when this substance does not correspond to levels suitable for human consumption, it can represent a means of transmitting diseases [1]. According to the World Health Organization – WHO (2016) [2], approximately half of the developing world population will be affected by infections directly related to water outside the quality standards either-or with lack of adequate or even non-existent sanitation.

The inappropriate disposal of residential waste, industrial, and agricultural effluents cause an imbalance in natural aquatic ecosystems. The amount of pollutants interferes with the proper functioning of the fauna and flora of these environments and, consequently, cause damage to the man himself [3]. Among the polluting agents of these ecosystems are pharmaceutical products, which are called emerging contaminants, of which antibiotics have been the subject of studies [4, 5].

Antibiotics are natural, synthetic, or semi-synthetic compounds developed and widely prescribed for therapeutic and prophylactic use against microbial infections in humans and animals [6, 7]. Besides, they have been widely used to stimulate the growth and production of animal [8–10]. The consumption of these drugs has increased considerably in recent decades, which is considered an emerging contaminant increasingly present in several environments, such as water [11, 12].

Despite being found in low concentrations in aquatic environments, data from the literature show that the presence of these contaminants causes negative impacts on several non-target organisms, such as microbial populations [13–15]. Changes in these populations can affect the maintenance of biological processes and change the structure of the entire ecosystem [16].

These drugs are considered the main source of changes in natural environments and influence a diversity of processes, including the development of antibiotic resistance and the spread of genes through horizontal gene transfer (HGT) [12, 17, 18]. Thus, the aquatic environment is considered efficient for the selection of bacterial populations resistant to antimicrobials, through mobile genetic elements [8]. Increased resistance to antimicrobials is often associated with a high adaptive capacity of microorganisms, with bacteria being more susceptible to changes and gene acquisition [19, 20].

Constant monitoring of bacterial communities is a tool that can lead to an understanding of the complexity of this phenomenon and the impact of human activities on natural environments [21]. In this context, this review aims to address the effects of antibiotics on microorganisms present in impacted aquatic environments.
