from a scientific view it is possible but I think registering the likely commercial product might be prohibited by law.

Yes, it is. Let´s take another viewpoint. Do you see any problem with a scientific article showing that red wine or a glass of whisky is beneficial to the heart? But the chances of developing health problems from excessive alcohol consumption are probably larger than from an oportunistic human pathogen.

This doesn´t mean that the article should recommend its use without a lot of further research, especially on the biosafety aspects, even without thinking about the legal side.

Many papers have shown that B. cepacia and other opportunistic pathogens have PGPB activity, but it is highly unlikely that these species would be registered for their plant growth promoting properties based on the reports of their prevalence in human tissues. I agree that some similarity exists with the red or whiskey analogy above, and like wine or whiskey, thorough study is necessary to prove biosafety. To my knowledge, not many investigations have been performed to demonstrate that some of these PGPBs, such as the plant-associated Burkholderias, e.g., B. unamae and others, are dangerous to animals. We are developing assays to do just that, but in these days of funding problems, progress is slow.

An organism that is both an opportunistic human pathogen and a plant growth-promoting rhizobacterium is still a growth-promoting rhizobacterium, so yes, it is. On the other hand, I should think that those who report that fact should mention its potential for pathogenicity, particularly if they are suggesting that the general public handle the rhizobacterium for some purpose.

I don't think it is appropriate to censure scientific publications simply because the organism is potentially pathogenic.

I definitely agree.

I think in developing countries where farmers are not much aware registering and marketing such products is not going to be safe. I can't say about developed countries. It will be better if we can bring anything new which should be human friendly because we should think about farmers also who are going to use the products and they may not be well aware of all the precautions.

If we observed in the nature by using pyrosequencing technique, then we might be surprise because such opportunistic bacteria dominate in the rhizosphere! Those bacteria are able to contribute on producing growth factors and nutrient cycling to provide nutrient to the plants. So those kind of papers are telling us the real function of the bacteria in the environment, then I would say that is OK.

I agree too, if the articles report PGPR as potential human pathogens, it doesnot mean that they suggest rhizobacteria as biocontrol agents, or growth stimulators because they cannot be registred. In our experience, during screening of root associated bacteria for their beneficial properties, we observed in the end, that majority of selected best strains belong to risk group and considered as potential human pathogens.

I'm directly working in this issue, with PGPR and biosecurity. It's right to report an opportunistic human pathogen as a PGPR, but if you are looking for a comertial product, you must take into account that in several cases it would be a very high difficulty introduce it in an agricultural explotation due to diseases and so. However, there are a lot of different pathogenic strains which are described as PGPR and are used as control/models in PGPR assays and in some farm cultivars (e.g. B. cepacia).

Very important topic for biotechnological commercial products! Not only B.cepacia. Recently, Stenotrophomonas maltophilia "moves" from the risk group 1 to the group 2. Some years ago a few countries, e.g. Germany and Japan, - changed " the risk status" for this bacteria. Obviously it is caused by the changes in the overal health (immune) status of human population, which is decreasing. So, isolation of strains with target properties (plant protection, growth stimulation, degradation of xenobiotics) is always connected with the the human safety context. By the way, working with ANY biopreparation is prohibited for persons with any type of allergy etc. Any microorganism is potentially harmful in high concentrations.

even we are observing similar opportunistic human pathogens such as "Pseudomonas aeruginosa" from the rhizosphere soil sample. even though it can be reported but its commercial utilization is still a question.it is interesting to study any difference between PGPR strain and pathogenic strain.

For study purpose and better understanding of soil microbiology you can do research on these organisms but If commercialization of these organisms as a product is difficult then why waste time. To be honest I am against using these organisms on large scale as a product. Perhaps you don't know what may go wrong and these organisms can spread diseases.

Yes I agree with Prof. Ann Hirsch that most of the rhizobacteria and even root nodule endophytes have showed PGP activity and many of them are human pathogens. Burkholderia species are common (B. cepacia; B. vietnamenensis etc) other than species of Enterobacter, Brucella's etc. In our studies with native legumes of Thar desert come across several examples where root nodule endophytes and bacteria of rhizoplan are of human pathogen and are showing PGP activities. Their registering as bio-control or PGPRs is a big question.

The population of such opportunistic pathogens is very high in the rhizosphere as refered by Sarjiya Antonius in his reply. These bugs are the real inhabitants of rhizosphere or they just replacing the orginal ones, because they can adept and compete well.....

I should correct my comments that such opportunistic pathogens are not always dominate but generally are found in the rhizosphere. Maybe its existence only by chance and they have a high adaptability. But whether these microbes have the ability to suppress the presence of microbial biodiversity, I do not know. I strongly agree that the microbes are not to be used in mass applications as biological fertilizers.

Dear praveen rahi, you cannot do that, because now all over the world, it has been restricted to report like that, for that you need to differentiate between the agriculture strain and clinical strain, then only people may accept......

There are no harmful microorganisms in ecosystems , there is a harmful abundance (activity) of microbial populations. Even rhizobia can sometimes harm.

Hi!!!

All bacteria are not harmful but there are pathogens, some are industrially important strains and some can become opportunistic bacteria when the host is immuno-suppressed. The bacteria found in soil are very diverse and it consists of pathogens from aerobic Pseudomonas to anaerobic Clostridium spp. As per your query the role of the bacteria as the plant-growth promoting hormone and opportunistic bacteria should be evaluated properly and also to be analysed which is the major role of bacteria and what are the factors that make the bacteria opportunistic human pathogen and whether these factors be monitored. You can mention about these in your report so that there is no questions raised on your research.

Secondly, if you are mentioning about opportunistic human pathogen than you have to mention about your lab bio-safety standards and produce a certificate to validate your findings.

The U.S. has definitely banned B. cepacia as a PGPB and Dr. Muter is correct that several bacteria have been moved from group 1 to group 2. However, many PGPB (such as nitrogen fixers) are also not human pathogens and have been used for centuries to improve plant growth, notably members of Rhizobiaceae. The larger question is how easy is it for genes to be exchanged among non-pathogenic species and pathogenic species within the same genus? This has not been answered, but yet it is an very important topic.

Is quite easy isthe exchange of genes among non-pathogenic species and pathogenic species within the same genus and more in the rhizosphere. It is being proved for plasmids found in this environment and in human

Definitely. In fact there are many cases of PGPRs pathogens. However, when using it must warn of potential risks as well as the necessary security means. I think Ann Hirsch aswer is correct at all.

It depends on the Regulatory Agency. but I think if you peformed toxicological and ecotoxicologycal tests and you can demostrate the strain is not pathogenic under many circunstances, then it can be used with security means.

Chemicals are more harmful (not only for humans, also for animals, water, environment) and they have been used and will be used for many years more.... green technologies will always be better for averybody

The most important point to consider a microorganism as "opportunistic human pathogen" is the place of isolation of the specific strain. Eg: there are reports of strains of Bacillus subtilis, Bacillus thuringiensis and Saccaromices cerevisceae as "opportunistic human pathogen"... however, there are many other strains widwly used as plant grrow promoters, bio pesticides and bred an wine production. The category of "opportunistic human pathogen", depends of many considerations and specific factors for each microorganism strain ...

An opportunistic pathogen is just that--opportunistic. It will more easily colonize an immunocompromised, physically weak host than an healthy one. Many of the PGPRs lack the classical pathogenicity genes that are characteristic of virulent strains. Now that we are in the age of genomics, it is not as difficult to begin to differentiate virulent from avirulent strains. However, we must recall that the interactions also depend a great deal on the state of the host and the balance between beneficial microbes and non-beneficial ones. My group is working on exactly this question.

Sorry, a grammatical error above. "a healthy one" is correct.

There is a distinction to be made here, in my point of view. The question is on reporting a PGPR which is ALSO an opportunistic pathogen.

From that point of view, I simply don´t have any issue that the correct answer is yes, especially if this possibility is clearly announced. That can only help to increase the database on the intersection of these groups and simplify works that try to understand both opportunistic pathogenity and PGPR mechanisms.

As for using or developing a product based on them, that´s another completely different subject, most probably decided on a per-country regulatory basis. Overall I doubt this would be generally prudent, even if legally allowed.

Mario,

Your point is well taken. B. cepacia and members of the BCC have pathogenicity-related genes and given a particular host, have the opportunity to colonize it. Other members of the same genus lack these elements and these are the ones that have potential for use in fields. i agree that developing a product based on potential opportunistic pathogens is not prudent.

The third group of microorganisms that can be found in the rhizosphere are true and opportunistic human pathogenic bacteria, which can be carried on or in plant tissue and may enhance plant growth and health, in particular the Enterobacteriaceae that can invade the root tissue (Mendes et al., 2013).

Non-plant pathogenic endophytic bacteria can promote plant growth, improve nitrogen nutrition, and, in some cases, are human pathogens such as enteric bacteria (Tyler and Triplett, 2008).

Mendes, R., Garbeva, P.,Raaijmakers, J. M. (2013). The rhizosphere microbiome: significance of plant beneficial, plant pathogenic, and human pathogenic microorganisms. FEMS Microbiology Reviews, 37(5), 634–663. doi:10.1111/1574-6976.12028

Tyler, H. L., Triplett, E. W. Plants as a habitat for beneficial and/or human pathogenic bacteria. Annu Rev Phytopathol 46, 53–73 (2008). DOI:10.1146/annurev.phyto.011708.103102

Yes. True and opportunistic human pathogenic bacteria may enhance plant growth, for example, the Enterobacteriaceae and I know that many people publish this. However, it would be difficult to use it in many countries, such as the US where, for example, Burkholderia cepacia species are not to be used for agriculture (U.S. Environmental Protection Agency 2003, Chiarini et al. 2006). See: Martínez-Hidalgo P, et al. Engineering root microbiomes for healthier crops and soils using beneficial, environmentally safe bacteria. 2018. Can. J. Microbiol. doi.org/10.1139/cjm-2018-0315. Frankly, I would not take the risk of using a potential pathogen. If we find such a strain, we will actually mention the risk in the publication. We want children to play in the "dirt" so they can build up their immune systems and normally the number of pathogens present in soil is low, so the risk is low of infection. If we add pathogens and increase their density beyond what are normally found in soil, this creates an increased risk and as a responsible scientist, I cannot do this.

Non-plant pathogenic endophytic bacteria can promote plant growth, improve nitrogen nutrition, and, in some cases, are human pathogens such as enteric bacteria (Tyler and Triplett, 2008). Dutta and Thakur (2017) also reported that PGPR in different field crops are considered as human opportunistic pathogens.

The third group of microorganisms that can be found in the rhizosphere are true and opportunistic human pathogenic bacteria, which can be carried on or in plant tissue and may enhance plant growth and health, in particular the Enterobacteriaceae that can invade the root tissue (Mendes et al., 2013).

Dutta, J., Thakur, D. (2017). Evaluation of multifarious plant growth promoting traits, antagonistic potential and phylogenetic affiliation of rhizobacteria associated with commercial tea plants grown in Darjeeling, India. PLOS ONE, 12(8), e0182302.doi:10.1371/journal.pone.0182302

Mendes, R., Garbeva, P.,Raaijmakers, J. M. (2013). The rhizosphere microbiome: significance of plant beneficial, plant pathogenic, and human pathogenic microorganisms. FEMS Microbiology Reviews, 37(5), 634–663. doi:10.1111/1574-6976.12028

Tyler, H. L., Triplett, E. W. Plants as a habitat for beneficial and/or human pathogenic bacteria. Annu Rev Phytopathol 46, 53–73 (2008). DOI:10.1146/annurev.phyto.011708.103102

Tomato growth and resistance promotion by Enterobacter hormaechei subsp. steigerwaltii EB8D , BENDAHA et al., 2019