How to sustainably feed a growing global population is a question still without an answer. Particularly farmers, to increase production, tend to apply more fertilizers and pesticides, a trend especially predominant in developing countries. Another challenge is that industrialization and other human activities produce pollutants, which accumulate in soils or aquatic environments, contaminating them. Not only is human well-being at risk, but also environmental health. Currently, recycling, land-filling, incineration and pyrolysis are being used to reduce the concentration of toxic pollutants from contaminated sites, but too have adverse effects on the environment, producing even more resistant and highly toxic intermediate compounds. Moreover, these methods are expensive, and are difficult to execute for soil, water, and air decontamination. Alternatively, green technologies are currently being developed to degrade toxic pollutants. This review provides an overview of current research on microbial inoculation as a way to either replace or reduce the use of agrochemicals and clean environments heavily affected by pollution. Microorganism-based inoculants that enhance nutrient uptake, promote crop growth, or protect plants from pests and diseases can replace agrochemicals in food production. Several examples of how biofertilizers and biopesticides enhance crop production are discussed. Plant roots can be colonized by a variety of favorable species and genera that promote plant growth. Microbial interventions can also be used to clean contaminated sites from accumulated pesticides, heavy metals, polyaromatic hydrocarbons, and other industrial effluents. The potential of and key processes used by microorganisms for sustainable development and environmental management are discussed in this review, followed by their future prospects.

/pdf/perspectives-of-microbial-inoculation-for-sustainable-4ecg9olcqc.pdf

Perspectives of Microbial Inoculation for Sustainable Development and Environmental Management.

Desert plants are able to survive under harsh environmental stresses inherent to arid and semiarid regions due to their association with bacterial endophytes. However, the identity, functions, and the factors that influence the association of bacterial endophytes with desert plants are poorly known. These bacterial endophytes can be used as an untapped resource to favor plant growth and development in agro-ecosystems of arid regions. The present study is therefore focused on the isolation and identification of bacterial endophytes from two native medicinal plants (Fagonia mollis Delile and Achillea fragrantissima (Forssk) Sch. Bip.) growing spontaneously in the arid region of the South Sinai (Egypt), and characterization of their plant growth promoting (PGP) traits. Thirteen putative bacterial endophytes were isolated from the leaves of both plant species and characterized for their plant growth promoting abilities using molecular and biochemical approaches, as well as greenhouse trials. Selected endophytic bacterial strains were applied to maize plants (Zea mays L. var. Single cross Pioneer 30K08) to further evaluate their PGP abilities under greenhouse conditions. Isolated bacterial strains have variable plant growth promoting activities. Among these activities, isolated bacterial endophytes have the efficacy of phosphate solubilizing with clear zones ranging from 7.6 ± 0.3 to 9.6 ± 0.3 mm. Additionally, the obtained bacterial endophytes increased the productivity of indole acetic acid (IAA) in broth media from 10 to 60 µg·mL−1 with increasing tryptophan concentration from 1 to 5 mg·mL−1. Bacillus and Brevibacillus strains were frequently isolated from the leaves of both plant species, and had significant positive effects on plant growth and shoot phosphorus (P) and nitrogen (N) contents. Results suggest that these endophytes are good candidates as plant growth promoting inoculants to help reduce chemical input in conventional agricultural practices and increase nutrient uptake and stress resilience in plant species.

Isolation and Characterization of Plant Growth Promoting Endophytic Bacteria from Desert Plants and Their Application as Bioinoculants for Sustainable Agriculture

Enterobacter sp. SA187 is an endophytic bacterium that has been isolated from root nodules of the indigenous desert plant Indigofera argentea. SA187 could survive in the rhizosphere as well as in association with different plant species, and was able to provide abiotic stress tolerance to Arabidopsis thaliana. The genome sequence of SA187 was obtained by using Pacific BioScience (PacBio) single-molecule sequencing technology, with average coverage of 275X. The genome of SA187 consists of one single 4,429,597 bp chromosome, with an average 56% GC content and 4,347 predicted protein coding DNA sequences (CDS), 153 ncRNA, 7 rRNA, and 84 tRNA. Functional analysis of the SA187 genome revealed a large number of genes involved in uptake and exchange of nutrients, chemotaxis, mobilization and plant colonization. A high number of genes were also found to be involved in survival, defense against oxidative stress and production of antimicrobial compounds and toxins. Moreover, different metabolic pathways were identified that potentially contribute to plant growth promotion. The information encoded in the genome of SA187 reveals the characteristics of a dualistic lifestyle of a bacterium that can adapt to different environments and promote the growth of plants. This information provides a better understanding of the mechanisms involved in plant-microbe interaction and could be further exploited to develop SA187 as a biological agent to improve agricultural practices in marginal and arid lands.

/pdf/complete-genome-sequence-analysis-of-enterobacter-sp-sa187-a-o2sy102drl.pdf

Complete Genome Sequence Analysis of Enterobacter sp. SA187, a Plant Multi-Stress Tolerance Promoting Endophytic Bacterium.

In this study, 15 bacterial endophytes linked with the leaves of the native medicinal plant Pulicaria incisa were isolated and identified as Agrobacterium fabrum, Acinetobacter radioresistant, Brevibacillus brevis, Bacillus cereus, Bacillus subtilis, Paenibacillus barengoltzii, and Burkholderia cepacia. These isolates exhibited variant tolerances to salt stress and showed high efficacy in indole-3-acetic acid (IAA) production in the absence/presence of tryptophan. The maximum productivity of IAA was recorded for B. cereus BI-8 and B. subtilis BI-10 with values of 117 ± 6 and 108 ± 4.6 μg mL−1, respectively, in the presence of 5 mg mL−1 tryptophan after 10 days. These two isolates had a high potential in phosphate solubilization and ammonia production, and they showed enzymatic activities for amylase, protease, xylanase, cellulase, chitinase, and catalase. In vitro antagonistic investigation showed their high efficacy against the three phytopathogens Fusarium oxysporum, Alternaria alternata, and Pythium ultimum, with inhibition percentages ranging from 20% ± 0.2% to 52.6% ± 0.2% (p ≤ 0.05). Therefore, these two endophytic bacteria were used as bio-inoculants for maize seeds, and the results showed that bacterial inoculations significantly increased the root length as well as the fresh and dry weights of the roots compared to the control plants. The Zea mays plant inoculated with the two endophytic strains BI-8 and BI-10 significantly improved (p ≤ 0.05) the growth performance as well as the nutrient uptake compared with an un-inoculated plant.

Plant Growth-Promoting Endophytic Bacterial Community Inhabiting the Leaves of Pulicaria incisa (Lam.) DC Inherent to Arid Regions

The objectives of this study were to assess actinobacterial diversity in five Moroccan extreme habitats and to evaluate their plant growth-promoting (PGP) activities. The soil samples were collected from different locations, including soils contaminated with heavy metals, from a high altitude site, from the desert, and from a marine environment. In total, 23 actinobacteria were isolated, 8 from Merzouga sand soil; 5 from Cannabis sativa rhizospheric soil; 5 from Toubkal mountain; 4 from a Draa sfar mining site; and 1 from marine soil. Based on their genotypic classification using 16S rRNA gene sequences, 19 of all belonged to the genus Streptomyces (82%) while the rest are the members of the genera Nocardioides (4.5%), Saccharomonospora (4.5%), Actinomadura (4.5%), and Prauserella (4.5%). Isolates Streptomyces sp. TNC-1 and Streptomyces sp. MNC-1 showed the highest level of phosphorus solubilization activity with 12.39 and 8.56 mg/mL, respectively. All 23 isolates were able to solubilize potassium, and 91% of them could grow under nitrogen-free conditions. The ability of the isolated actinobacteria to form indole-3-acetic acid (IAA) ranged from 6.70 to 75.54 μg/mL with Streptomyces sp. MNC-1 being the best IAA producer. In addition, all of the actinobacteria could produce siderophores, with Saccharomonospora sp. LNS-1 synthesizing the greatest amount (138.92 μg/mL). Principal coordinate analysis revealed that Streptomyces spp. MNC-1, MNT-1, MNB-2, and KNC-5; Saccharomonospora sp. LNS-1; and Nocardioides sp. KNC-3 each showed a variety of high-level plant growth-promoting activities. The extreme environments in Morocco are rich with bioactive actinobacteria that possess a variety of plant growth-promoting potentials that can further benefit green and sustainable agriculture.

https://www.mdpi.com/1424-2818/11/8/139/pdf

Actinobacteria from Extreme Niches in Morocco and Their Plant Growth-Promoting Potentials

Microorganisms play a vital role in maintaining soil fertility and plant health. They can act as biofertilizers and increase the resistance to biotic and abiotic stress. This study aimed at isolating and characterizing plant growth-promoting bacteria associated with sugarcane, as well as assessing their ability to promote plant growth. Endophytic bacteria from leaf, stem, root and rhizosphere were isolated from the RB 867515 commercial sugarcane variety and screened for indole acetic acid (IAA) production, ability to solubilize phosphate, fix nitrogen and produce hydrogen cyanide (HCN), ammonia and the enzymes pectinase, cellulase and chitinase. A total of 136 bacteria were isolated, with 83 of them presenting some plant growth mechanism: 47 % phosphate solubilizers, 26 % nitrogen fixers and 57 % producing IAA, 0.7 % HCN and chitinase, 45 % ammonia, 30 % cellulose and 8 % pectinase. The seven best isolates were tested for their ability to promote plant growth in maize. The isolates tested for plant growth promotion belong to the Enterobacteriaceae family and the Klebsiella, Enterobacter and Pantoea genera. Five isolates promoted plant growth in greenhouse experiments, showing potential as biofertilizers.

/pdf/isolation-and-selection-of-plant-growth-promoting-bacteria-qrmuby2ajf.pdf

Isolation and selection of plant growth-promoting bacteria associated with sugarcane

Microorganisms associated with organic management are essential in nutrient transformation and release for plant use. The present study aimed to isolate, identify and characterize plant growth promoting diazotrophic rhizobacteria associated with sugarcane under organic management. Rhizospheres of organic sugarcane varieties IAC 911099 and CTC4 were sampled and inoculated onto nitrogen free NFb and Burk media. The isolated microorganisms were screened in vitro concerning their ability to produce plant growth promoting factors. Eighty-one bacteria were isolated; 45.6% were positive for the nifH gene and produced at least one of the evaluated plant growth promotion factors. The production of indole-3-acetic acid was observed in 46% of the isolates, while phosphate solubilization was observed in 86.5%. No isolates were hydrogen cyanide producers, while 81% were ammonia producers, 19% produced cellulases and 2.7%, chitinases. Microorganisms belonging to the Burkholderia genus were able to inhibit Fusarium moniliforme growth in vitro. Plant growth promoting microorganisms associated with organic sugarcane, especially belonging to Burkholderia, Sphingobium, Rhizobium and Enterobacter genera, can be environmentally friendly alternatives to improve sugarcane production.

/pdf/isolation-and-prospection-of-diazotrophic-rhizobacteria-3rvw64olbw.pdf

Isolation and prospection of diazotrophic rhizobacteria associated with sugarcane under organic management

/pdf/isolation-and-screening-for-multi-trait-plant-growth-349avwvhf3.pdf

Isolation and Screening for Multi-trait Plant Growth Promoting Actinobacteria From Organic Sugarcane Rhizosphere

A biomineralizacao e uma alteracao quimica em um ambiente atraves de atividademicrobiana que resulta na precipitacao de minerais, sendo um fenomenoamplamente distribuido na natureza. Na precipitacao de carbonato de calcioinduzida microbiologicamente (MICP, do ingles microbially induced calciumcarbonate precipitation), a urease apresenta papel importante ao hidrolisar a ureia,por uma grande variedade de micro-organismos capazes de produzir elevadosniveis desta enzima. Existem diferentes polimorfos do cristal de carbonato de calcioe a estrutura que e formada depende do tipo da fonte de calcio utilizada, periodo deincubacao e atividades metabolicas referentes a especie microbiana avaliada. AMICP e uma alternativa promissora e ambientalmente amigavel para as tecnologiasde remediacao atuais e convencionais capazes de resolverem problemas ambientaisem campos multidisciplinares. Varias aplicacoes como aumento da qualidade e damelhoria das propriedades de materiais de construcao, remocao de metaispotencialmente toxicos e radionucleotideos e sequestro de dioxido de carbonoatmosferico tem sido discutidas.

/pdf/bioprecipitacao-de-carbonato-de-calcio-por-bacterias-xdi90dca24.pdf

Bioprecipitação de carbonato de cálcio por bactérias ureolíticas e suas aplicações

Phenolic compounds are common pollutants in industrial effluents and pose a significant risk to the environment. The microbial capacity to degrade these molecules makes the prospection of bacteria with this ability very strategic for bioremediation processes in contaminated areas. This study was carried out to isolate bacteria with phenol degrading capacity from Brazilian mangrove soil. Microorganisms were evaluated for tolerance and the ability to use this substance as a single source of carbon. Two bacterial isolates were obtained: MF-1 and MF-2. The microorganisms were identified, respectively, as Bacillus cereus and Bacillus circulans by sequencing the 16S rRNA gene. The isolates exhibited tolerance to phenol at concentrations up to 600 mg.L-1 when grown in Bushnell-Haas Agar (BHA) and 1,500 mg.L-1 in nutrient agar (NA). As for the use of phenol as a single carbon source, the microorganisms were grown in concentrations of 100, 200 and 300 mg.L-1 of the compound. The isolate MF-1 presented a percentage consumption of 22.43, 11.52 and 3.33%, respectively, for each tested concentration. Although there was a decrease in phenol consumption in response to the increased concentration of this substance, bacterial growth was not affected. The best results were obtained for the isolate MF-2, in which consumption of phenol was, respectively, 21.54, 20.54 and 28.85% for these concentrations. Likewise, the increase in phenol concentration caused no reduction in the growth of this isolate.

	 

	Key words: Bioremediation, xenobiotic, phenol degrading bacteria, mangrove.

/pdf/isolation-and-characterization-of-phenol-degrading-bacillus-385d10np41.pdf

Ariana Alves Rodrigues

Papers

Isolation and selection of plant growth-promoting bacteria associated with sugarcane

Isolation and prospection of diazotrophic rhizobacteria associated with sugarcane under organic management

Isolation and Screening for Multi-trait Plant Growth Promoting Actinobacteria From Organic Sugarcane Rhizosphere

Bioprecipitação de carbonato de cálcio por bactérias ureolíticas e suas aplicações

Isolation and characterization of phenol degrading Bacillus species from a Southeast Brazilian mangrove sediment