Is Our Use of Antibiotics Creating More Resistant, Virulent Bacterial Strains?

By: Alexandra Ortiz 

Human Gut and Environmental Metagenomic Comparison. Schematic overview of the comparative study of the human gut and environmental metagenomes. Researchers mined in the genes of the human gut and environmental bacterial communities to understand the relationship between antibiotic resistance genes and virulence factors (VFs). Their efforts were able to show that there is a link between the dissemination of VFs and antibiotic resistance. 

Over the years, our excessive use of antibiotics in both medicine and agriculture has selected for antibiotic-resistant bacterial strains in human and environmental communities. Although pathogenic bacteria are the targets of antibiotics, nonpathogenic bacteria are affected in antibiotic contaminated environments. Pathogenic bacteria use virulence factors for parasitizing hosts that include proteins for adhesion and invasion of tissues, secretion of toxins and iron acquisition systems. Interestingly, environmental bacteria use these virulence factors (VFs) to adhere and colonize different surfaces, compete with other bacteria, and access resources such as iron. Escudiero et al. (2019) conducted a comparative study between environmental and human gut microbial communities from different human populations across the world to identify differences between and among the sampled communities. They were able to find a higher diversity of antibiotic resistance (AR) and VFs in environmental samples when compared to human gut samples. However, human fecal microbiomes had a higher accumulation of AR than environmental communities. This research was also able to catch a glimpse of what the pre-antibiotic era of the human resistome looks like in uncontacted Ameridian gut microbiome samples. Lastly, the correlation found between AR and VF diversity in both human and environmental samples suggests that as our use of antibiotics continues, we may be selecting for more virulent, resistant bacteria. 

Beneficial Bacteria Give it Away for Drought Resistant Chili Pepper Plants

By: Alexandra Ortiz

The Use of Plant-Growth Promoting Bacteria for Drought-Resistant Crops.  Overview of how plant-growth-promoting bacteria (PGPB) play a role in defending the chili pepper plant from drought stress. PGPBs can serve as biostimulants by reducing the levels of stress hormones produced and biofertilizers by making limiting nutrients such as phosphate and iron more available for plants. Root colonization is important in PGPBs for critical plant-bacterial interactions such as the production of specialized compounds that prevent desiccation. Image source: Alexandra Ortiz.

Drought is one of the largest causes of crop yield losses across the world. With increasing demands for water, there is a need to expand biotechnological approaches for the development of drought-resistant plants or the use of drought-resistant plant growth-promoting microorganisms. Horticultural crops such as chili peppers are extremely sensitive to moisture stress, specifically in the root zone, therefore, water is crucial for the cultivation of these high-value crops (Walters and Jha, 2016). Vigani and colleagues proposed the use of two known plant growth-promoting pepper associated bacteria to defend the plant from dry conditions in a hydroponic and terrestrial system. They suggested that the bacteria’s plant growth-promoting characteristics that allow for enhanced nutrient availability, reduced stress hormone production, and root colonization abilities coupled with resistance to drought conditions would enhance the pepper plant’s survival under low moisture conditions. They were able to find that pepper plants grown in drought-stressed hydroponic systems that were subjected to the bacteria had no visible symptoms of drought stress. In soil, drought-stressed plants showed no significant differences in biomass when compared to the irrigated, uninoculated plants. Therefore, Vigani et al., (2019) were able to utilize these bacteria to protect the pepper plants from drought in soil and hydroponic systems.

References

Walters, S.A., and A.K. Jha. (2016). Sustaining Chili Pepper Production in Afghanistan through Better Irrigation Practices and Management. Agriculture 6(4), 62.