Enumeration of Citrus endophytic bacterial communities based on illumine metagenomics technique

Citrus is a valuable crop in Pakistan because it is rich in vitamin C and antioxidants. Huanglongbing (HLB) has an influence on citrus production around the world caused by a bacterium “ Candidatus liberibacter asiaticus ” (CLas), africanus and americanus. The structure and diversity of bacterial species in various ecosystems can be quickly examined using NGS. This approach is considerably quicker and more precise than outdated methods. Healthy or citrus greening infected leaf samples of Grapefruit, Citrus aurantifolia , and Citrus reticulata Blanco was used for diversity analysis. In this study high throughput, NGS technique was used to access the population of both cultivable and non-cultivable bacterial endophytes from citrus leaves, by using PCR amplicons of 16S rDNA sequences (V5–V7 regions) with Illumina Hi seq. As a result, a total number of 68,722 sequences were produced from the test samples. According to the NGS-based diversity classification, the most common genera of exploited bacterial endophytes were Proteobacteria, Firmicutes, Bacteroides, Cyanobacteria, and Actinobacteria. Citrus aurantifolia and Citrus paradisi showed almost equal diversity, whereas Citrus reticulata Blanco had a higher proportion of Proteobacteria and Cyanobacteria in their leaves. To determine alpha diversity (AD), additional data was analyzed using statistical indices such as Shannon, Chao1, and Simpson. According to the inverse Simpson diversity index, the abundance of the microbial population in six different citrus samples was 0.48, 0.567, and 0.163, respectively. The metagenomics of microbiota in plant tissues was successfully recorded by NGS technology, which can help us learn more about the interactions between plants and microbes. This research is the first step toward a better understanding of 16SrRNA-based metagenomics from citrus in Pakistan using Illumina (Hi seq) Technology.

Pharmacological Properties, Volatile Organic Compounds, and Genome Sequences of Bacterial Endophytes from the Mangrove Plant Rhizophora apiculata Blume

Mangrove plant endophytic bacteria are prolific sources of bioactive secondary metabolites. In the present study, twenty-three endophytic bacteria were isolated from the fresh roots of the mangrove plant Rhizophora apiculata. The identification of isolates by 16S rRNA gene sequences revealed that the isolated endophytic bacteria belonged to nine genera, including Streptomyces, Bacillus, Pseudovibrio, Microbacterium, Brevibacterium, Microbulbifer, Micrococcus, Rossellomorea, and Paracoccus. The ethyl acetate extracts of the endophytic bacteria’s pharmacological properties were evaluated in vitro, including antimicrobial, antioxidant, α-amylase and α-glucosidase inhibitory, xanthine oxidase inhibitory, and cytotoxic activities. Gas chromatography–mass spectrometry (GC-MS) analyses of three high bioactive strains Bacillus sp. RAR_GA_16, Rossellomorea vietnamensis RAR_WA_32, and Bacillus sp. RAR_M1_44 identified major volatile organic compounds (VOCs) in their ethyl acetate extracts. Genome analyses identified biosynthesis gene clusters (BGCs) of secondary metabolites of the bacterial endophytes. The obtained results reveal that the endophytic bacteria from R. apiculata may be a potential source of pharmacological secondary metabolites, and further investigations of the high bioactive strains—such as fermentation and isolation of pure bioactive compounds, and heterologous expression of novel BGCs in appropriate expression hosts—may allow exploring and exploiting the promising bioactive compounds for future drug development.

Evaluation of Inorganic Phosphate Solubilizing Efficiency and Multiple Plant Growth Promoting Properties of Endophytic Bacteria Isolated From Root Nodules Erythrina Brucei

Background: The majority of phosphorous in the soil is fixed and unavailable to plant nutrition, hence in scarcity. Phosphate solubilizing bacteria, the ecological engineers, are considered as the best, sustainable and eco-friendly options. The objectives of this study were to screen and evaluate inorganic phosphate solubilizing efficiency and assess multiple plant growth promoting traits of E. brucei root nodule bacterial endophytes.Results: A total of 304 nodule bacterial endophytes were screened for phosphate solubilization potential on solid PA medium among which 119 (39%) were potential tricalcium phosphate solubilizers. None of these isolates were able to form clearly visible halos on aluminum phosphate (AlPO4), Al-P or iron phosphate (FePO4), Fe-P supplemented PA medium. Out of 119 inorganic phosphate solubilizing endophytes, 40.3% were IAA producers. Based on phosphate solubilization index, the potential bacterial endophytes were identified to Gluconobacter cerinus, Acinetobacter soli, Achromobacter xylosoxidans and Bacillus thuringiensis using the 16S rRNA gene sequences analysis. All the selected isolates were potential solubilizers of the three inorganic phosphates (Al-P, Fe-P and tricalcium phosphate, TCP) included in liquid NBRIP medium. The highest values of solubilized TCP were recorded by isolates AU4 and RG6 (A. soli), 108.96 mg L-1 and 107.48 mg L-1, respectively at sampling day3 and 120.36 mg L-1 and 112.82 mg L-1, respectively at day 6. The highest values of solubilized Al-P and Fe-P were recorded by isolate RG6, 102.14 mg L-1 and 96.07 mg L-1, respectively at sampling days 3 and 6, respectively. The highest IAA, 313.61µg mL-1 was recorded by isolate DM17 (B. thuringiensis). These selected potential isolates were also HCN, NH3, and hydrolytic enzymes producers. The isolates were also varied in tolerance to eco-physiological stressors and exhibited versatility to carbon and nitrogen substrate utilization. Conclusions: The genera and species Gluconobacter cerinus, Acinetobacter soli, Achromobacter xylosoxidans and Bacillus thuringiensis are the first reports from E .brucei root nodules and Gluconobacter is also the first report to the science as phosphate solubilizer. Isolates AU4 and RG (A. soli) could be potential bio-inoculant candidates for the growth enhancement of the host plant for better agro-forestry practices in acidic and alkaline soils in Ethiopia.