Introduction

The Ganges water has been consumed from time immemorial for domestic as well as remedial purposes. It is well known that, over the years, the Ganga water has become inadequate and unsafe for drinking. The Ganga River is home to a large population of pathogenic bacterial species. But still, the river water continues to be used for domestic purposes and, surprisingly, the effects are not as deadly as expected. The reason behind this peculiarity is expected to be the presence of virome in the river Ganga. This review revolves around the interaction of virome present in the Ganges with the pathogenic bacteriome and with the river water consumers. It aims at highlighting the mechanisms involved in the protective roles played by virome against severe waterborne diseases. It further aims to present a few findings that propose that Ganges Water contributes novel antimicrobial aspects which have the possibility to deliver a need basis for the progress of novel antibacterial components in near future.

Outreaches of Ganga

Ganga is the great river of the plains of the northern Indian subcontinent. The Ganga River originates from the confluence of the Bhagirathi and Alaknanda at Devaprayag town of Uttarakhand. The Alaknanda River emerges from the foot of Gangotri Glacier at Gomukh in the western Himalayas. It drains one-fourth of the Indian Territory and finally drains into the Sunderbans delta in the Bay of Bengal (Fig 1).

Figure 1: Map showing the flow of Ganga. Click here to view figure

The Present Condition of the River Ganga

The ever-increasing population and urbanization in the river basin is leading to organic carbon buildup and high environmental deposition. The DO level of the river water depletes substantially due to tannery effluents¹. Increased BOD values (≥5.2ppm) ² are for the straight flow of sewage material in the river and the establishment of a large number of apartments, industries, and hospitals on the river banks ³ making its water unfit for drinking and refreshment.

The river water remains highly contaminated through sewage and tannery effluents are treated ⁴. Ganga has high coliform contamination (5–20 times more than the tolerable limit) and high Cultivable Vibrios Count mainly for the direct flow of sewage and open removal around the banks of the river. Due to this reason, the annual periodic diarrheal recurrences in monsoon and post-monsoon seasons in South Bengal are initiated. The microbial and chemical contamination are caused mainly by rapid industrialization and urbanization throughout the river banks which impose an immense threat to human health ⁵.

The Major Causes of Pollution in Ganga

A large amount of untreated waste disposal in the Ganges is due to the lack of functional treatment plants. 6.7% of cities and towns have limited sewage treatment and 0.25% have complete sewage treatment ⁶ (Fig 2), of which most are primarily useless because of lack of functionality by construction and upkeep, absence of workforce, poor management, and deficiency of constant electricity ⁷. Feces in open areas can make their way into streams easily and overflows causing contamination of nutrition sources ⁸. Almost 1 billion liters of untreated sewage are dumped in the river daily which has doubled in the last 20 years and another 100% increase in the next 20 years is predicted ⁹.

Figure 2: Variations in Dissolved Oxygen Levels and Biological Oxygen Demands Over The Years From 2011 to 2016[5] Click here to view figure

Pristine Nature of the Ganges

Ganga Vs Other Indian Rivers

A study established that the river Ganga is the most pristine of all the Indian rivers ^6. Although the presence of pathogens, heavy metals, and other toxicities are higher in Ganga as compared to other rivers, still Ganga retains its purity due to the fact that it contains a great number of bacteriophages as compared to Narmada and Yamuna ^2.

Self-Purificatory Aspects of Ganga

So far this review has discussed about the level of contamination in the Ganges, the major causes of pollution in the river and how these factors contribute to make Ganges a severe threat to our health. High amounts of Enteropathogens are deposited in Ganges having high potential to cause fatal health issues in children and adults residing in the banks of the Ganges, children being at higher risk than adults. So, a very high rate of disease occurrence and infectivity is expected to result from the consumption of Ganga water.

However, the reality is different. In the past it was proven that the Ganges retains a self-purifying capacity ² that is derived from its inquisitively high capacity to maintain dissolved oxygen ^10. Lack of suitable DO leads to infected condition and causes increases BOD in the river ^9. The maintenance of high DO levels is performed by specific bacteriophages which feed on certain bacterial population of the river, thus lowering its pathogenic load.

The Call for the Use of Virome against Enteropathogens of Ganges

Several studies have shown that the Ganges exhibit much higher levels of Bacteriophages than any other river of the country which correlates with the self-purificatory properties of Ganga. Bacteriophages being able to lyse the bacterial cells and affect their population seem to have a very significant role in lowering the level of contaminants in the Ganges and bringing down the risk of serious health hazards. E. coli is a desired indicator for freshwater recreation. It’s presence gives straight evidence of fecal contamination from warm-blooded animals. The anti-microbial agent resistance profile provides the evidence that river Ganga is a source of multiple-antimicrobial-resistant E.coli ¹¹. E.coli isolates from urban areas have resistance to more antibiotics than rural isolates possibly due to greater contact to antibiotics. E. coli may transfer between virulent and non-virulent making these forms indistinguishable from normal gut flora ^12.

A study on Multi-Drug Resistant Bacteria in the Ganga surface waters of Kolkata detected Superbugs which are resistant to multiple drugs ^13. More than 2000 tons antibiotics are made these days and MDR bacteria are maximum at the industry sites and its adjacent river. In Escherichia coli and Pseudomonas aeruginosa, many drug efflux genes are assembled which resemble the ABC transporter genes ¹⁴ (Fig 3).

Figure 3: Total Coliform and Fecal Coliform Variations in Ganga Over The Years From 2007 to 2016[5] Click here to view figure

The severity of heavy metal contamination can be indicated very well by the presence of the microbial community ^15. The lower and middle stretches of Ganga have high microbial and heavy metal contamination ¹⁶. Further, some bacterial species which are available in Ganga water, like Bacillus cereus, B. thuringiensis and B. subtilis, are identified to reduce hexavalent chromium (CrVI), a toxic and carcinogenic form, to the non-toxic trivalent chromium (CrIII) ¹⁷. This again indicates the curative properties of Ganges because CrIII is a necessary nutrient that stimulates metabolism of glucose, fat and protein by helping the activity of insulin in humans and animals ¹⁸. Ganga reveals certain distinct qualities of higher alkalinity and pH and presence of trace elements. These have a role in self-purificatory properties of river Ganga by influencing the growth of bacteriophages. Phages usually need divalent metal ions for their growth, again their stability, attaching to the host cell for the entry of their nucleic acid and multiplication all are controlled by the ions ^19.

All these evidences call for study about the implications of virome. Virome seems to have strong contribution in the curative properties of Ganga water.

Why to Rely on Virome?

Several types of purifying activities have been adopted to have a pathogen-free Ganga, but none have been proved to be effective enough. However, a natural purification mechanism has been observed in the Ganges in several studies time and again. Some of which are listed below.

In 1896, Ernest Hankin found phages that thrived in tap water, died in non-boiled but filtered Ganges water and also died in boiled Ganges water ^20.

In 1916, Felix d’Herelle identified factors which are heat labile and difficult to filter but exhibit antimicrobial activity ^21.

IIT Roorkee in 2019, isolated Superphage from Ganga, decoded lysine gene and cloned lysine protein with great potential as antibacterial pharmaceutical ^22.

CSIR identified >20 types of phages in Ganges that fight microbes which cause TB, pneumonia, cholera etc ^23.

Nature and Components of the Human Gut Virome

The human gut virome is usually individual specific and can be stable for one year. A persistent personal virome usually present in the most stable fraction of viruses of any individual and that can be linked to highly predominant gut bacterial taxa ^24.

Effect of Gut Virome in Homeostasis and Dysbiosis

The mammalian intestinal virome usually consist of viruses which can multiply in both eukaryotic and prokaryotic cells. The virome activates a mutual relationship with eukaryotes or prokaryotes. It contribute to intestinal homeostasis after inducing host immunity and microbial ecology. The pathogenesis of some diseases via microbial host lysis may lead to dysbiosis and that can be contributed by the virome ^25.

Many bacterial species inhabiting our Gastro-Intestinal track are beneficial for us which maintain a quite stable population in the human gut, the normal microbiota of our gut. However, this normal microflora gets imbalanced under certain cases, like during the course of antibiotics which is prevented by the human gut virome. Viruses provide antibiotic resistance via Horizontal Gene Transfer (HGT). HGT also leads to the occurrence of virulence in the bacterial species which triggers immune response in the host generating Reactive Oxygen Species, which in turn triggers more HGT. Antibiotics also cause induction of prophage and lysis of commensals resulting in pathogenic bacterial species to invade the host tissues due to elimination of competition. So, a supplement for use of antibiotic is necessary, which is provided by Phage Therapy. Phage Therapy can be administered to kill pathogens. Latent viral infection causes immune activation and prevents pathogenic infection and removal of pathogens. Thus a Phage-Mediated Immunity is generated ^26.

Thus, interactions of viruses with the host immune system as well as the commensal bacteriome of the host are both positively and negatively regulated ²⁷. More studies will reveal the proper mechanisms of these interactions and how these interactions can be directed for the advent of human utility.

The functional role of viruses in humans and animals is not known clearly till date. One hypothesis concludes that few of these viruses influence on human health indirectly by eradicating viral pathogens through viral intervention or by cross-immunity ^28. It has been revealed that patients with HIV and hepatitis G virus interrupt the manifestation of AIDS ^29. Though, few viruses proliferate the risk of secondary infection by an analogous virulent genotype or new microbial/viral agents by maintaining chronic inflammation or stimulating virus-related carcinogenesis in particulars with a particular immunological disorder ^30. Different agents of the Papillomaviridae, Polyomaviridae, and Herpesviridae families have been associated with cancers in humans. ^31,32,33,34.

So, it can be concluded that interactions of viruses with humans go after simple parasitism. Several eukaryotic viruses can have persistent interactions with their counterpart. The beneficial or adverse effects of such interactions may be determined by the structural site of infection, the genotype of host or immune status, or the existence of other microbes and Viruses.

Methods of detection of Viruses or VLPs from the Ganges

Now that such a huge level of viral utility is estimated to be already occurring naturally in the Ganges as well as in our gut, it becomes highly necessary to have proper techniques to detect, isolate and identify Viruses or VLPs from the river water sample so that using them we can take a step towards making Ganga pathogen-free. This will help in making the use of Ganga water for various purposes safer. Various methods are already in use which detects viral samples from water samples. Some of which are PCR (RT PCR, qPCR), flow cytometry, MPN studies, plaque assays, observation of cytopathogenic effects, metagenome-based pathogen surveillance etc. The already in use methods need to be practiced more efficiently and many more methods need to be introduced for studying the vast array of virus-mediated Ganges purification.

Conclusion

It has been established and widely accepted that Ganga has self-purificatory activities owing to the presence of certain viral strains into the water. The high abundance of the virome in the Ganges as compared to other rivers sheds light on this belief. Certain viruses are capable of digesting pollutants and contaminants including heavy metals and dangerous pathogens. Due to the presence of these kinds of viruses along with deadly pathogens and high order pollutants in the Ganges, the use of the river water is not life-threatening.  Although much more shreds of evidence are required for the proper implementation of virome-mediated purification projects on the river. It is necessary to identify those viral species which are directly or indirectly involved in cleansing actions of the Ganges and use them for cleaning the river, making it pathogen-free and thus safer for domestic, agricultural as well as industrial use.

Acknowledgement

Authors thank to DST-SERB, Govt. of India and Department of Biotechnology West Bengal Govt. for financial assistance.

Conflict of Interest

Author declare that they have no conflict of interest.

Funding Source

The work was supported by DST-SERB, Govt. of India.

References

1. Bhatnagar, M. K., Singh, R., Gupta, S., & Bhatnagar, P. Study of tannery effluents and its effects on sediments of river Ganga in special reference to heavy metals at Jajmau Kanpur, India. Journal of Environmental Research and Development. 2010; 8 (1), 56–59.
2. Ayesha Mariya & Chitranjan Kumar & Mohd. Masood & Niraj Kumar. The pristine nature of river Ganges: its qualitative deterioration and suggestive restoration strategies, Environmental Monitoring and Assessment.2019;
   CrossRef
3. ENVIS Centre on Control of Pollution Water Air and Noise. Central Pollution Control Board, Ministry of Environment and Forests, Government of India: http://www.cpcbenvis.nic.in/water_quality_data.html#. Accessed 8 June 2020.
4. Sushil Kumar Singh, Manish Kumar Kanth, Dhirendra Kumar, Rishikesh Raj, Abhijeet Kashyap, Pranav Kumar Jha, Ashutosh Anand, Kumari Puja, Suman Kumari, Yusuf Ali, Ram Shiv Lokesh, Shivam Kumar. Analysis of Water Quality of River Ganga from Digha Ghat to Gai Ghat in Patna District, Bihar, India. J. Life. Sci. Scienti. Res. 2017; 3(5): 1350-1354.
   CrossRef
5. Suvajit Saha, Madhumanti Halder, Subham Mookerjee, Anup Palit (2019), Seasonal influence, enteropathogenic microbial load and diarrheal enigma in the Gangetic Delta, India: Present scenario and health implications. J Infect Public Health. 2019; 12(4):540-548.
   CrossRef
6. https://en.wikipedia.org/wiki/Water_pollution_in_India, Accessed on 11^th August 2020
7. http://www.cseindia.org/userfiles/aagd2013_report.pdf, Accessed on 11^th August 2020
8. http://www.bbc.com/news/health-33980904, Accessed on 11th August 2020
9. Das S. Cleaning of the Ganga. Journal Geological Society of India. 2011;78:124-130
   CrossRef
10. Wetzel R.G., Likens G.E. Limnological analysis, 3rd ed. Springer-Verlag, New York, 391. 2006.
11. Water Contamination: A Growing Epidemic. https://microbewiki.kenyon.edu/index.php/ Water_Contamination:_A_Growing_ Epidemic Accessed on 12^th August 2020
12. Siya Ram, Poornima Vajpayee and Rishi Shanker (2007), Prevalence of Multi-Antimicrobial-Agent Resistant, Shiga Toxin and Enterotoxin Producing Escherichia coli in Surface Waters of River Ganga, Environmental Science & Technology. 2007; 41(21), 7383-7388
    CrossRef
13. Hacker, J.; Blum-Oehler, G.; Mu¨hldorfer, I.; Tscha¨pe, H. Pathogenicity islands of virulent bacteria: structure, function and impact on microbiological evolution. Mol. Microbiol. 1997; 23, 1089-1097.
    CrossRef
14. Asit Kumar Chakraborty, Kousik Poira, Debashray Saha, C. Halder, S. Das and S. Nandi Multidrug-Resistant Bacteria with Activated and Diversified MDR Genes in Kolkata Water: Ganga Action Plan and Heterogeneous Phyto-Antibiotics Tackling Superbug Spread in India, 2018 DOI: 10.13140/RG.2.2.17947.52001.
15. McArthur AG, Waglechner N, Nizam F, Bhullara K, et al. The comprehensive antibiotic resistance database. Antimicrob Agents Chemther. 2013; 57: 3348-3357.
    CrossRef
16. Zhang, Y., Li, H., Gong, L., Dong, G., Shen, L., Wang, Y., et al. Nano-sized Fe2O3/Fe3O4 facilitates anaerobic transformation of hexavalent chromium in soil–water systems. Journal of Environmental Sciences. 2017; 57, 329–337
    CrossRef
17. Dwivedi, S., Mishra, S., & Tripathi, R. D. Ganga water pollution: a potential health threat to inhabitants of Ganga basin. Environment International. 2018;117, 327–338
    CrossRef
18. Upadhyay, N., Vishwakarma, K., Singh, J., Mishra, M., Kumar, V., Rani, R., & Sharma, S.Tolerance and reduction of chromium (VI) by Bacillus sp. MNU16 isolated from contaminated coal mining soil. Frontiers in Plant Science.2017; 8, 778.
    CrossRef
19. Sanjay Dwivedi & Puneet Singh Chauhan & Seema Mishra & Amit Kumar & Pradyumna Kumar Singh & Mohan Kamthan & Reshu Chauhan & Surabhi Awasthi & Sumit Yadav & Aradhana Mishra & Shekhar Mallick & Sanjeev Kumar Ojha & Sri Krishna Tewari & Rudra Deo Tripathi & Chandra Shekhar Nautiyal. Self-cleansing properties of Ganga during mass ritualistic bathing on Maha-Kumbh. Environmental Monitoring and Assessment. 2020; 192 (221). DOI: 10.1007/s10661-020-8152-2.
    CrossRef
20. Rakhuba, D. V., Kolomiets, E. I., Dey, E. S., & Novik, G. I. Bacteriophage receptors, mechanisms of phage adsorption and penetration into host cell. Polish Journal of Microbiology. 2010; 59, 145–155
    CrossRef
21. https://iasgatewayy.com/ganga-has-higher-proportion-of-antibacterial-agents/
22. https://iasgatewayy.com/ganga-has-higher-proportion-of-antibacterial-agents/
23. https://www.thehindu.com/news/national/ganga-has-higher-proportion-of-antibacterial-agents-study/article26890979.ece
24. https://timesofindia.indiatimes.com/city/chandigarh/Polluted-Ganga-has-healing-touch-thanks-to-viruses/articleshow/54504431.cms
25. Andrey N. Shkoporov, Adam G. Clooney, Thomas D.S. Sutton, Vimalkumar Velayudhan, R. Paul Ross, Colin Hill (2019). The Human Gut Virome Is Highly Diverse, Stable, and Individual Specific. Cell host & Microbe. 2019; 26, 527-541.
    CrossRef
26. R. Carding, N. Davis, L. Hoyles. The Human Intestinal Virome in Health and Disease. Alimentary Pharmacology and Therapeutics. 2017; DOI: 10.1111/apt.14280.
    CrossRef
27. Aislinn D. Rowan-Nash, Benjamin J. Korry, Eleftherios Mylonakis, Peter Belenky (2019). Cross-Domain and Viral Interactions in the Microbiome. Microbiology and Molecular Biology Reviews. 2019; 83(1); DOI:1128/MMBR.00044-18.
    CrossRef
28. Carolina Domínguez-Díaz, Alejandra García-Orozco, Annie Riera-Leal1, Jorge Ricardo Padilla-Arellano and Mary Fafutis-Morris. Microbiota and Its Role on Viral Evasion: Is It With Us or Against Us? Front Cell Infect Microbiol. 2019; DOI: 10.3389/fcimb.2019.00256.
    CrossRef
29. Barton ES, White DW, Cathelyn JS, Brett-McClellan KA, Engle M, et al. Herpesvirus latency confers symbiotic protection from bacterial infection. 2007; 447:326–29.
    CrossRef
30. Bhattarai N, Stapleton JT. GB virus C: The good boy virus? Trends Microbiol. 2012; 20:124–30.
    CrossRef
31. McLaughlin-DrubinME, Munger K. (2008). Viruses associated with human cancer. Biophys. Acta. 2008; 1782:127–50.
    CrossRef
32. Nicol´as Rascovan, Raja Duraisamy, and Christelle Desnues (2016). Metagenomics and the Human Virome in Asymptomatic Individuals. Annu Rev Microbiol. 2016; 70:125-41.
    CrossRef
33. Xu B, Li F, Cai L, Zhang R, Fan L, Zhang C. A holistic genome dataset of bacteria, archaea and viruses of the Pearl River estuary. Sci Data. 2022; 9(1):49.
    CrossRef
34. Adriaenssens EM, Farkas K, McDonald JE, Jones DL, Allison HE, McCarthy AJ. Tracing the fate of wastewater viruses reveals catchment-scale virome diversity and connectivity. Water Res. 2021; 203:117568. doi: 10.1016/j.watres.2021.117568.
    CrossRef