Effects of Multiple-Metal-Compound Contamination on the Soil Microbial Community in Typical Karst Tea Plantations

Round 1

Reviewer 1 Report

dear authors,

Your manuscript is interesting and brings new values to science. The work is well written but has some shortcomings.

Here are some notes:

1. using only abbreviations of research objects makes the manuscript difficult to read. please add explanations under the tables and figures.

2. in my opinion, the methodology is insufficiently described because it does not correspond to the discussed results (e.g. data in table 2 and subchapter 3.4). please check and complete it.

3. line 243: should be superscript.

Good luck,

reviewer

Author Response

Dear reviewer,

Thank you very much for your comments and suggestions, which are very valuable for us to improve the manuscript and study. According to your helpful comments and suggestions, we have carefully revised the manuscript.

1. using only abbreviations of research objects makes the manuscript difficult to read. please add explanations under the tables and figures.

Response：Thank you very much for your suggestions. We have added explanations under the first figures (first occurrence). The change as follow: (line 220-222)

Note: PH was the tea plantation on plateau hills, UF was the tea plantation Under forests, LR was the tea plantation surround the Lakeside and SS was the tea plantation on steep slope. (the same below).

2. in my opinion, the methodology is insufficiently described because it does not correspond to the discussed results (e.g. data in table 2 and subchapter 3.4). please check and complete it.

Response: We are thankful for your kind reminding. We have strengthened the part of methodology about microbial contents, and the change as follow: (line 186-196)

2.3.2 Soil microbial diversity and community structure

After sequencing all samples, Circular Consensus Sequencing (CCS) sequences were obtained through Barcode recognition. The CCS sequences were screened and clustered to identify effective CCS, and then classified as OTUs. OTU clustering involves clustering sequences at a similarity level of 97% using USEARCH (version 10.0) and filtering OTUs with a threshold of 0.005% of all sequences [57-58]. The numbers of phylum, class, order, family, genus, and species were determined based on the results of OTUs, after than the microbial community structure and cluster were analyzed further more. QIIME2 software was used to analyze alpha diversity, which represents the microbial diversity and abundance within a specific area, single sample or ecosystem. This analysis included metrics such as Chao1, Ace, Shannon, Simpson index, and others.

3. line 243: should be superscript.

Response: We are thankful for your kind reminding. We have revised the unit of g·kg^-1 as superscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have worked on "Effects of multiple metal compound .......tea plantations". The authors have done good work.

I have few queries.

1. What is the effect of a particular metal on a particular group of bacteria?

2. What could be the reason for impact of heavy metal pollution on soil microbial diversity?

3. Line 94. Italicize the Campylobacter.

Author Response

Dear reviewer,

Thank you very much for your comments and suggestions, which are very valuable for us to improve the manuscript. According to your helpful comments and suggestions, we have carefully revised the manuscript. 

1. What is the effect of a particular metal on a particular group of bacteria?

Responses: Thank you very much for your valuable comments and suggestions. We have enhanced the description of a particular metal's effect on a specific group of bacteria, and we have added figures 7b/c/d/e to clarify the correlation between the particular metal and the specific microbial genus. The add text as follow:  (line 564-574)

According to the relationship between line length and included angle between heavy metals and dominant genera [6], there was a significant positional correlation between Puia_din and Cu, Cr, Zn; ADurbBin0 and Ni, Cr, Zn, and Cd; and Acidobac and Cr and Ni. The relationship between Acidipil and Cd, Occallat and Cr and Zn showed a significant negative correlation (figure 7a). These results reveal that there were different effective of a particular metal on a particular group of bacteria. Among, Ni, Cd and Cu can significant positive promote the abundance of ADurbBin0, Acidobac and Puia_din respectively, however the effective of Cd on Acidipil was negative (figure 7b/c/d/e).

a	b
c	d
e

Figure 7. The effect of a particular metal on a particular microbial genus: a) The top 10 soil microbial genera in response to heavy metals in all samples. b), c), d), and e) represent the correlation between particular metal and particular microbial genus.

2. What could be the reason for impact of heavy metal pollution on soil microbial diversity?

Responses: Thank you very much for your valuable comments and suggestions.We have strengthened the reason for impact of heavy metal pollution on soil microbial diversity. The revised as follow: (line 548-553)

According to the information shown in Figure 2a, all different types of tea plantations were generally polluted by Cd and Hg simultaneously. However, LR was also found to be polluted by Cu and Cr. Changes in microbial communities caused by Cd and Cu pollution may affect the diversity of metabolic functions [62]. Cu is typically present in soil as a trace element, serving as a component of microbial enzymes and participating in microbial metabolic processes. Adequate copper levels can promote the growth and metabolic activity of soil microorganisms [63]. The soil microbial genus Acidipila_silvibacterium was commonly found in all different types of tea plantations. The heavy metal Cu was positively impacted by Cd and Hg, and the tea plantation soil was also polluted by Cd and Hg. So, an important reason for the impact of heavy metal pollution on soil microbial diversity is that the heavy metal Cu influences the components of microbial enzymes and microbial metabolic processes. In addition, soil heavy metal pollution impacts the proportion of the dominant microbial structure, which in turn further influences soil microbial diversity.

3. Line 94. Italicize the Campylobacter.

Responses: Thank you very much for your valuable comments and suggestions.We have change  the format of all bacteria in our manuscript, make it Italicize.

 

Author Response File: Author Response.pdf