Let's Ask the Soil

It makes sense right? Scientists are always talking about how the problem is not that we do not have enough phosphorus; the problem is that most of what we have is unavailable to plants. Ok… so let’s just transform the phosphorus we have into a form plants can use and call it a day...

                 

 

          

This is exactly the thinking behind a recent study in the Microbiology Biotechnology Journal. The basic premise of this paper was to isolate and evaluate phosphate-solubilizing bacteria (PSB) from soil and note any significant changes that may take place in the harsh environmental conditions of some crops' soil.

The paper explains that in agriculture, P is only available to plants in its soluble forms of phosphate ion (Pi), HPO4- or H2PO-. Most soil normally contains about 400–1,200 mg/kg, which is way beyond what any plant requires. However, it combines with other elements in the soil and forms  organic and inorganic compounds that plants can’t utilize. However, some specific bacteria have been known to remove the phosphate from these compounds. This would allow plants to absorb the phosphate freely. 


The authors of the paper now transition from the introduction into the method section. They explain that crop soil was extracted and the PSBs were isolated. 16S rDNA amplification and sequencing was performed to verify that it was in fact PSBs that were isolated. The PSBs were then studied under harsh conditions such as high-salt concentrations, extreme temperatures and varying acidity. 


The results of this paper are very easy to follow just by looking at a few, although very basic, graphs (see below for some examples). Truth be told, the whole paper could probably be summed up by simply analyzing these graphs. All the PSB strains survived at high temperatures. Most PSBs could tolerate added NaCl to as much as 2.5%. It was also observed that these bacteria favor alkaline conditions

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“In conclusion, we have isolated several PSB strains, three of which were more promising for being used as Pi biofertilizers,” stated Malboobi at the end of this particular research.

In terms of content, this paper falls short in many aspects. None of the genomic work is covered or explained, and the study itself is lacking numerous biochemical details in the method section. As a Master’s student, I am constantly reading current literature and looking to other papers’ methods to follow. It would be extremely difficult to repeat these experiments based on the details provided. In particular, they do not even mention how they performed the phosphatase activity assays. This simple vital information cannot be left out of such a "credible" journal.

 The paper also fails to provide any form of a literature review. They do not cover the work of any other scientists attempting this same type of biochemical approach. The paper does bring in some research to support its conclusions, but the scope of the paper is very narrow and it sticks to very basic past research. I am sure Malboobi and his colleagues are not the ONLY researchers working on this topic. However, you would not know this by simply reading the article.

Alright, enough with the negatives.

At the end of the day, this research has immense promise. Bacteria are easy to replicate, manipulate, and study. Less chemical fertilizer would be needed, and the environment would only benefit from these types of solutions. Blue green bacteria have already been used as biofertilizer in rice cultivation on a small scale. However, the technology for producing these inoculants on a large scale is not as simple. 


But hey, two steps forward and one step back. 

Reference 

Malboobi MA, Owlia P, Behbahani M, Sarokhani E, Moradi S, Yakhchali B, Deljou A, Heravi KM (2009). Solubilization of organic and inorganic phosphates by three highly efficient soil bacterial isolates. World J.
Microbiol. Biotechnol., 25: 1471-1477.