Antibiotic Resistant Genes in Your Water!?

By Ruby Ayala

The experimental design of three transformation model systems designed to assess the effects of chlorine-based disinfectants on the spread of antibiotic-resistant genes. The figure is taken from Zhang et al. (2021)

Antibiotic-resistant bacteria are a rising threat to public health worldwide. Chlorination is a method of disinfection that has been widely used to inactivate bacteria and pathogens in wastewater treatment plants; however, the disinfection process can damage antibiotic-resistant bacteria and result in the release of antibiotic-resistant genes into the water that would be readily available for uptake by other bacteria through their cellular membrane. In a study by Zhang and colleagues (2021), they used plasmid-encoded antibiotic-resistant genes and a recipient bacteria in three different transformation systems to determine whether chlorination influenced the spread of antibiotic-resistant genes in conditions mimicking drinking water and the effluent of wastewater treatments. After verifying the recipient bacteria took up the plasmid and showed signs of resistance to two antibiotics, ampicillin and tetracycline, the results revealed that at relevant concentrations, chlorine-based disinfection can promote the natural transformation of antibiotic-resistant genes among bacteria found in water. This could be attributed to the fact that disinfection induces a series of cell responses and bacterial membrane damage that enhance the bacteria's uptake of antibiotic-resistant genes. The findings of this study give scientists a better understanding of the role of disinfectants and their relation to the dispersal of antibiotic resistance in bacteria. With the knowledge gained, better management of disinfection practices in water systems can be strategized and applied to protect the health of humans and future generations.

Original article: 

Zhang S, Wang Y, Lu J, Yu Z, Song H, Bond PL, Guo J. 2021. Chlorine disinfection facilitates natural transformation through ROS-mediated oxidative stress. The ISME Journal 15:2969-2985. 

Saving the Honey Bees with Bacteria

 By Ruby Ayala

A honey bee with a Varroa mite. Photo taken by Alex Wild from The University of Texas at Austin

Honey bees are very critical pollinators and play a huge role in global food production. Without honey bees, dozens of agricultural crops ranging from fruits to nuts to vegetables would either decrease substantially or vanish all together. Unfortunately, our friendly neighborhood pollinators are experiencing wide population declines due to parasites, such as Varroa mites, and pathogens, such as the RNA virus that causes wing deformity. The increasing loss of the honey bees has become a problem for agriculture; therefore, Leonard and colleagues from the University of Texas at Austin conducted a study wherein they evaluated the honey bee's survival rate after having engineered bacteria that inhabit their gut microbiome to combat varroa mite infestations and wing deformity. The team engineered two different bacterial strains for the honey bees to ingest; one that targets the RNA virus and one that targets the Varroa mites. The engineered bacteria have a symbiotic relationship with the honeybee and produce double-stranded DNA that alters gene expression and triggers RNA interference immune responses. The results of the study showed that compared with the control bees, the bees with wing deformity treated with the engineered bacterial strain were 36.5% more likely to survive a longer period of time (10 days). Also, the Varroa mites on bees treated with the mite-targeting strain were 70% more likely to die compared to the mites feeding on the control bees. The findings of this research not only provide a possible solution to decrease the loss of honey bee populations but also gives other researchers an insight into how bacteria can be altered to save other species from disease.

Original article:

Leonard SP, Powell JE, Perutka J, Geng P, Heckmann LC, Horak RD, Davies BW, Ellington AD, Barrick JE, Moran NA. 2020. Engineered Symbionts Activate Honey Bee Immunity and Limit Pathogens. Science 367:573-576.

Deep-Sea Deep Sequencing: A Showcase of Extraordinary Viral Diversity

 By: Umberto Fasci

 

Phylogenetic analysis of viral contigs from marine sediments, marine water, freshwater and terrestrial soil - proteome-wide similarity relationships. Figure taken from Zheng et al. 2021.

 

 This study with the fascinating aim to improve the knowledge of the virosphere in deep-sea sediments, investigates the viral diversity at both gene and genomic levels in the deep-sea sediments of the Southwest Indian Ocean. This alone seems ambitious. However, with the decreasing cost and increasing data acquisition of sequencing technologies, deep sequencing has become valuable for this use case. From their deep sequencing analysis, the researchers here found a large number of unclassified viral groups with a total of 1106 viral contigs. Amazingly, 217 of these expressed complete viral genomes with none clustered with any known viral genome. It was also found that over two thirds of the ORFs within these viral contigs encode for no known functions. This by itself is extraordinary, suggesting the the deep-sea sediments represent an enormous site for novel viral genotypes. Ultimately, this study opens a box which requires the right tools to access. With this, future related studies should explore how the novel viral metabolic genes found here may be involved in energy production, or amino acid synthesis pathways at this level of the marine environment. Elucidating this may improve our understanding of how involved these novel viral genes are in the marine sediment environment.

 

 

Zheng, X., Liu, W., Dai, X., Zhu, Yaxin, Wang, J., Zhu, Y., et al. (2021) Extraordinary diversity of viruses in deep-sea sediments as revealed by metagenomics without prior virion separation. Environ Microbiol 23: 728–743.

 

Lacking Phosphorus? These Microbes Might be the Answer

 By: Umberto Fasci

 

The distribution and activity of isolated PSMicro strains in bamboo rhizosphere. A. Isolated PSmicro strains in bamboo rhizosphere. B. Relative abundances of isolated PSMicro strains in bamboo rhizosphere. C. Variation in phosphorus solubilization by Pseudomonas sp. in bamboo rhizosphere. D. Variation in phosphorus solubilization by Burkholderia sp. in bamboo rhizosphere. Figure taken from Xing et al. 2021.

To understand the importance of what this study investigates, I will illuminate the importance of phosphorus-solubilizing microorganisms (PSMicros). PSMicros are essential in assisting associated plants to resist phosphorus deficiency in soils. On the whole, this study investigates the microbial diversity of PSMicro strains from several bamboo rhizosphere sites. The study showed great variation in microbial diversity between these bamboo rhizosphere sites where 52 PSMicro strains were isolated and identified. Among these isolations, 10 bacteria genera and 4 fungal genera were identified. From this, the researchers of this study found that Bacillus, Kluyvera, Buttiauxella, Meyerozyma and Penicillium species were most readily utilized to supply plant-usable phosphorus from both organic and inorganic phosphorus sources. As such, this study identifies PSMicro strains which can be possibly used in ecosystem restoration. A good step for future research into this subject should take these results as reference, and to conduct a more thorough investigation with metagenomic techniques. The potential impacts alone this study has should inspire future research as such.

Xing, Y., Shi, W., Zhu, Y., Wang, F., Wu, H., and Ying, Y. (2021) Screening and activity assessing of phosphorus availability improving microorganisms associated with bamboo rhizosphere in subtropical China. Environ Microbiol 23: 6074–6088.

Bacteria that Aid in Petroleum Polluted Soil

 By: Melissa Villareal 

The figure shows the residual Naphthalene (NAP) percentage after an 8 day incubation. By day 8, there was a significant reduction of the percentage of NAP compared to the sterile control group. Figure taken from Cai et al. 2021.

Environment pollution is an increasing problem with industrialization and globalization. The world relies on petroleum to operate machinery and vehicles. This can lead to petroleum contamination in soil, and it is a serious problem. Petroleum contamination contain organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) that pose a serious threat to human health. PAHs are toxic and can cause cancer, DNA mutations and other serious effects on health.

A study by Cai and colleagues (2021) identified a bacteria species that can degrade a type of PAH called naphthalene (NAP). This uncultured bacteria is a Gamma-Proteobacterium species, and it is a key NAP degrader. This is a form of bioremediation mechanism that is found in the natural environment. Their metabolism is able to break down this organic pollutant.

The next step of this research is to identify more bio-degraders of PAH, and being able to culture these bacteria species. Overall, this research is very important to efficiently and safely clean up pollutants from the soil. This can prevent human health consequences, and protect the ecosystem.    

Original Article:

Cai, X., Li, J., Guan, F., Luo, X.and Yuan, Y. (2021) Unveiling metabolic characteristics of an uncultured Gammaproteobacterium responsible for in situ  PAH biodegradation in petroleum polluted soil. Environ Microbiol.

Soil Bacteria Can Fight Climate Change

 By: Melissa Villareal 

The figure shows the detected microbial communities from the three desert plant species. The red points represent the same microbes shared by the three desert plants. Figure taken from Sun et al. 2021.

Climate change has increased the desertification of arid regions. Desertification is the process by which fertile areas degrade and lose bio-productivity. The lands become infertile and hostile to plants and animals. This rapid increase of desertification poses an environmental threat. 

Desert plants can aid in recolonizing desert areas to combat the loss of biodiversity. Three desert plant species continue to thrive even under increased stress caused by climate change because they have high adaptability. A study by Sun and colleagues (2021) show that the microbiota living in these desert plants are key to their survival. These bacteria provide essential nutrients, aid in plant hormone production and protect the hosts from harmful pathogens. These bacteria species can sustain plant growth under extreme abiotic stress! So far two bacteria species have been identified: Streptomyces eurythermus and Streptomyces flaveus. 

Finding methods to combat desertification is important to maintain biodiversity in these arid areas, and offers possible solutions in desert management. Lastly, studying bacterial communities that aid in plant growth in extreme abiotic stress can help the agriculture industries. Microbial tools can increase agricultural productivity in a safer and more sustainable way.

Original Article:

Sun, X., Pei, J., Zhao, L., Ahmad, B.and Huang, L. (2021) Fighting climate change: soil bacteria communities and topography play a role in plant colonization of desert areas. Environ Microbiol.