First insights into the rhizospheric bacterial abundance data of Ceriops tagal (Perr.) C.B.Rob. from Indian Sundarbans

This article reports the analyses of the rhizospheric microbiome of the terrestrial mangrove Ceriops tagal (Perr.) C.B.Rob. from the Indian Sundarbans. Samples were collected using standard protocols and 16S rRNA gene V3–V4 region amplicon sequencing was performed to identify the bacterial communities prevalent in the rhizosphere. A total of 1,74,324 quality checked reads were assembled into contigs and were analyzed using QIIME2 and MetaG server to reveal the abundance of Proteobacteria, Bacteroidetes and Actinobacteria. The data is available at the NCBI - Sequence Read Archive with accession number: SRR15652592. This is the first report of the rhizospheric microbiome belonging to this plant from the Indian Sundarbans.


Specifications
Biological

Value of the Data
• The importance of this data lies in that it is a data amounting to the first report of bacterial abundance using 16S rRNA sequencing using NGS platforms in the rhizosphere of Ceriops tagal (Perr.) C.B.Rob. from the Indian Sundarbans, which can be used for future comparative metagenomic analyses. • Ceriops tagal (Perr.) C.B.Rob. is one of the most important true mangrove species of the Indian Sundarbans which is fast declining from populated islands. Thus, a proper idea in terms of it's rhizospheric bacterial assemblage would help us to analyse the factors that are contributing towards it's habitat loss. • The data is valuable for the purposes of ecological monitoring of the Indian Sundarbans which is currently under the onslaught of increasing cyclonic activities and salinity ingression into agricultural land [1] . • The data will enhance and augment ongoing mangrove restoration approaches and practices [2] which will help to curb accelerated loss of deltaic soil in the Indian Sundarbans and will benefit the indigenous human population and fauna by assisting fertile land reclamation and land recovery.

Data Description
The paired end reads uploaded on the Nephele server returned a complete QC analysis of the data. The QC statistics are listed in the Table 1 . MetaG server data outputs were classified according to the taxonomic ranks of the OTU clusters. Of the 1,74,406 OTUs, 82 failed to pass the QC filter and 1,74,324 OTUs were matched to reference, all of which were found to be of bacterial origin, explaining the nature of dominant domain composition of the rhizospheric soil sample of Ceriops tagal (Perr.) C.B.Rob. The alphadiversity of this data set was identified to be 9.181, with the Shannon diversity index value of 4.298 and Faith's Phylogenetic Diversity (PD) index value at 8.380. The phylum level data exhibits the highest abundance of Proteobacteria (79.8%), followed by Bacteroidetes (12.5%), Actinobacteria (4.9%), Firmicutes (2.05%), Cyanobacteria (0.46%), Planctomycetes (0.15%) and Chloroflexi (0.04%) respectively with unclassified bacterial sequences amounting to 0.16%. Of the phylum Proteobacteria, Gammaproteobacteria (49.3%) and Alphaproteobacteria (12.5%) was found to contribute majorly to the class level abundance. Deltaproteobacteria (10%) and Betapropteobacteria (7.85%) also ranked in majority only to be flanked by Flavobacteria (11.9%). Class Actinobacteria (4.9%) and Bacilli (1.1%) was found to follow the preceding members.
The family level data of the sample exhibited the presence of Halomonadaceae (22.6%) as the major constituent of all the family of bacteria present. Pseudomonadaceae (11.96%), Flavobacteriaceae (11.89%), Bacteriovoracaceae (9.82%), Moraxellaceae (8.49%), Caulobacteraceae (8.05%) and Rhodocyclaceae (5.58%) respectively contribute significantly to the family level abundance data along with others. The Family-level abundance is represented in the bar graph as Fig. 1 .

Rhizospheric soil collection and metagenomic sequencing
The 16S rRNA gene consists of nine hypervariable regions interspersed between conserved regions, which has found widespread usage in identifying and characterizing the bacterial community of an environmental sample. In the present analysis, microbial community structure was identified by targeting V3-V4 region, as these regions show high variability which helps to distinguish bacterial subtypes.

Collection of sample
Maximum population density of Ceriops tagal (Perr.) C.B.Rob. at a specific site was used to determine the sampling site. The soil was deltaic alluvium with a slightly acidic pH and heavytextured with a mixture of silt, sand, clay and mud. Rhizospheric soil sample was collected from an appropriate depth beneath the muddy swamp base that is less prone to the semi-diurnal tidal inundation. Sample collection was performed wearing gloves and mask to reduce any chance of anthropogenic contamination. The soil sample was placed in a sterile zip lock packet and kept in an ice box at 4 °C for preservation.

Preparation of sample
An in-house standardized protocol was used for isolation of genomic DNA from a rhizospheric sample. DNA quality was assessed by Nanodrop and on agarose gel, followed by quantification using QUBIT. The library preparation was carried out using Illumina standardized V3-V4 regions of the 16S rRNA library protocol. The enriched library was quantified and validated using qPCR and Agilent Bioanalyzer (DNA 10 0 0 chip). The library generated containing V3-V4 amplicons was sequenced on Illumina MiSeq using 300 × 2 PE chemistry.

Bioinformatic analyses
The Bioinformatics pipeline previously reported in [3] was used to analyze the data. The quality control of raw reads was carried out using the FASTQC toolkit ( http://www.bioinformatics. babraham.ac.uk/projects/fastqc ) via the Nephele: Microbiome Analysis site ( https://nephele.niaid. nih.gov/ ). The quality processed paired end reads were clustered into OTU's (Operational Taxonomic Units) by using QIIME2 software to identify the microbial community.
The processed reads were uploaded to MetaG server ( http://www.bioinformatics. uni-muenster.de/tools/metag/index.hbi ) for analysis and classification of abundant bacteria to the classification level of Genus and Krona graphs [4] were generated for visualization.

Ethics Statements
Not applicable.

CRediT Author Statement
GAD and SG performed the sample collection and processing. SG and BM conceptualized the methodology workflow and GAD performed the analyses. SG and BM were involved in overall supervision of the work.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data Availability
Ceriops Tagal Rhizosphere (Original data) (NCBI -SRA). the funds provided for DNA Sequencing by the Department of Science & Technology, West Bengal. The authors acknowledge the contributions of Mr. Pinaki Mandal, for his help during sample collection.