Molecular characterization of nitrogen-fixing bacteria isolated from brazilian agricultural plants at São Paulo state

Isolation and Characterization of Multi-Trait Plant Growth-Promoting Endophytic Bacteria from Scots Pine Tissues

Scots pine (Pinus sylvestris) is a globally significant tree species with considerable economic importance in forestry. A major challenge in afforestation, particularly in stressful environments, is growing seedlings with high viability and stress resistance. Recent studies suggest that Pseudomonas strains can alleviate stress and promote growth in crops, though limited evidence exists for trees. This study aimed to assess the plant growth-promoting (PGP) properties of Pseudomonas strains isolated from Scots pine stems using in vitro assays, and to evaluate their potential as bioinoculants through a two-year long field trial. From over sixty bacterial isolates originating from Scots pine stem tissues, only four were selected as being similar to Pseudomonas bacteria. Through 16S rRNA gene sequencing, the isolates were identified as Pseudomonas putida P57, Pseudomonas lurida P88 and 10-1, and Stenotrophomonas maltophilia P77. All isolates inhibited fungal pathogens Botrytis cinerea and Fusarium sporotrichiella, and exhibited PGP activities including nitrogen fixation and production of IAA (1.24-17.74 mg/l), ammonia (4.06-12.71 μM/ml), and siderophores, with the highest value of 1.44 ± 0.19 for the P. lurida P88 strain. Additionally, the Pseudomonas strains demonstrated phosphate solubilization capacity. We revealed that bioinoculation with strains P57 and P88 enhanced field germination of seeds by 35-45% and increased aerial biomass of two-year-old seedlings by 80-140%. Both strains adhered to seed surface and colonized roots and stems at levels of 2.4-3.2 log CFU/g fresh tissue up to two years post-inoculation. These findings highlight the potential of these bacterial strains as effective bioinoculants for improving Scots pine seedling growth under natural conditions.

Wild Wheat Rhizosphere-Associated Plant Growth-Promoting Bacteria Exudates: Effect on Root Development in Modern Wheat and Composition

Diazotrophic bacteria isolated from the rhizosphere of a wild wheat ancestor, grown from its refuge area in the Fertile Crescent, were found to be efficient Plant Growth-Promoting Rhizobacteria (PGPR), upon interaction with an elite wheat cultivar. In nitrogen-starved plants, they increased the amount of nitrogen in the seed crop (per plant) by about twofold. A bacterial growth medium was developed to investigate the effects of bacterial exudates on root development in the elite cultivar, and to analyze the exo-metabolomes and exo-proteomes. Altered root development was observed, with distinct responses depending on the strain, for instance, with respect to root hair development. A first conclusion from these results is that the ability of wheat to establish effective beneficial interactions with PGPRs does not appear to have undergone systematic deep reprogramming during domestication. Exo-metabolome analysis revealed a complex set of secondary metabolites, including nutrient ion chelators, cyclopeptides that could act as phytohormone mimetics, and quorum sensing molecules having inter-kingdom signaling properties. The exo-proteome-comprised strain-specific enzymes, and structural proteins belonging to outer-membrane vesicles, are likely to sequester metabolites in their lumen. Thus, the methodological processes we have developed to collect and analyze bacterial exudates have revealed that PGPRs constitutively exude a highly complex set of metabolites; this is likely to allow numerous mechanisms to simultaneously contribute to plant growth promotion, and thereby to also broaden the spectra of plant genotypes (species and accessions/cultivars) with which beneficial interactions can occur.

Pseudomonas aeruginosa Ld-08 isolated from Lilium davidii exhibits antifungal and growth-promoting properties

A plant growth-promoting and antifungal endophytic bacteria designated as Ld-08 isolated from the bulbs of Lilium davidii was identified as Pseudomonas aeruginosa based on phenotypic, microscopic, and 16S rRNA gene sequence analysis. Ld-08 exhibited antifungal effects against Fusarium oxysporum, Botrytis cinerea, Botryosphaeria dothidea, and Fusarium fujikuroi. Ld-08 showed the highest growth inhibition, i.e., 83.82±4.76% against B. dothidea followed by 74.12±3.87%, 67.56±3.35%, and 63.67±3.39% against F. fujikuroi, B. cinerea, and F. oxysporum, respectively. The ethyl acetate fraction of Ld-08 revealed the presence of several bioactive secondary metabolites. Prominent compounds were quinolones; 3,9-dimethoxypterocarpan; cascaroside B; dehydroabietylamine; epiandrosterone; nocodazole; oxolinic acid; pyochelin; rhodotulic acid; 9,12-octadecadienoic acid; di-peptides; tri-peptides; ursodiol, and venlafaxine. The strain Ld-08 showed organic acids, ACC deaminase, phosphate solubilization, IAA, and siderophore. The sterilized bulbs of a Lilium variety, inoculated with Ld-08, were further studied for plant growth-promoting traits. The inoculated plants showed improved growth than the control plants. Importantly, some growth parameters such as plant height, leaf length, bulb weight, and root length were significantly (P ≤0.05) increased in the inoculated plants than in the control un-inoculated plants. Further investigations are required to explore the potential of this strain to be used as a plant growth-promoting and biocontrol agent in sustainable agriculture.

Isolation, identification and characterization of nitrogen fixing endophytic bacteria and their effects on cassava production

BACKGROUND

Cassava (Manibot esculenta Crantz) is one of the most important among tuber crops. The amount of nitrogen fertilizer used for cassava production is relatively high (400 kg ha^-1), but there are few studies on biological nitrogen fixation in this crop. Therefore, it is particularly important to study whether cassava and microorganisms have the associated nitrogen-fixing and other promoting effects of endophytic bacteria.

METHODS

We screened 10 endophytic bacteria using the nitrogen-free culture method from the roots of seven cassava cultivars, and the nitrogenase activity of the A02 strain was the highest 95.81 nmol mL^-1 h^-1. The A02 strain was confirmed as Microbacteriaceae, Curtobacterium using 16S rRNA sequence alignment. The biological and morphological characteristics of strain A02 were further analyzed.

RESULTS

The experimental results showed that the biomass of roots, stems, and leaves of cassava inoculated with A02 increased by 17.6%, 12.6%, and 10.3%, respectively, compared to that of the control (without A02 inoculation). These results were not only related to the secretion of auxin (IAA) and solubilization of phosphate but also in the promotion of biological nitrogen fixation of cassava leaves by strain A02. Moreover, the highest 95.81 nmol mL^-1h^-1 of nitrogenase activity was reported in strain A02, and thus more nitrogen fixation was observed in strain A02. In conclusion, A02 is a newly discovered endophytic nitrogen-fixing bacteria in cassava that can be further used in the research of biological bacterial fertilizers.

Performance of halotolerant bacteria associated with Sahara-inhabiting halophytes Atriplex halimus L. and Lygeum spartum L. ameliorate tomato plant growth and tolerance to saline stress: from selective isolation to genomic analysis of potential determinants

The use of halotolerant beneficial plant-growth-promoting (PGP) bacteria is considered as a promising eco-friendly approach to improve the salt tolerance of cash crops. One strategy to enhance the possibility of obtaining stress-alleviating bacteria is to screen salt impacted soils. In this study, amongst the 40 endophytic bacteria isolated from the roots of Sahara-inhabiting halophytes Atriplex halimus L. and Lygeum spartum L., 8 showed interesting NaCl tolerance in vitro. Their evaluation, through different tomato plant trials, permitted the isolate IS26 to be distinguished as the most effective seed inoculum for both plant growth promotion and mitigation of salt stress. On the basis of 16S rRNA gene sequence, the isolate was closely related to Stenotrophomonas rhizophila. It was then screened in vitro for multiple PGP traits and the strain-complete genome was sequenced and analysed to further decipher the genomic basis of the putative mechanisms underlying its osmoprotective and plant growth abilities. A remarkable number of genes putatively involved in mechanisms responsible for rhizosphere colonization, plant association, strong competition for nutrients, and the production of important plant growth regulator compounds, such as AIA and spermidine, were highlighted, as were substances protecting against stress, including different osmolytes like trehalose, glucosylglycerol, proline, and glycine betaine. By having genes related to complementary mechanisms of osmosensing, osmoregulation and osmoprotection, the strain confirmed its great capacity to adapt to highly saline environments. Moreover, the presence of various genes potentially related to multiple enzymatic antioxidant processes, able to reduce salt-induced overproduction of ROS, was also detected.

The natural recovery of soil microbial community and nitrogen functions after pasture abandonment in the Amazon region

We assessed the impacts of forest-to-pasture conversion on the dynamic of soil microbial communities, especially those involved in the N-cycle, and their potential functions, using DNA-metagenomic sequencing coupled with the quantification of marker genes for N-cycling. We also evaluated whether the community's dynamic was reestablished with secondary forest growth. In general, the microbial community structure was influenced by changes in soil chemical properties. Aluminum and nitrate significantly correlated to community structure and with 12 out of 21 microbial phyla. The N-related microbial groups and their potential functions were also affected by land-use change, with pasture being clearly different from primary and secondary forest systems. The microbial community analysis demonstrated that forest-to-pasture conversion increased the abundance of different microbial groups related to nitrogen fixation, including Bacteroidetes, Chloroflexi and Firmicutes. In contrast, after pasture abandonment and with the secondary forest regeneration, there was an increase in the abundance of Proteobacteria taxa and denitrification genes. Our multi-analytical approach indicated that the secondary forest presented some signs of resilience, suggesting that the N-related microbial groups and their potential functions can be recovered over time with implications for future ecological restoration programs.

Potential PGPR Properties of Cellulolytic, Nitrogen-Fixing, Phosphate-Solubilizing Bacteria in Rehabilitated Tropical Forest Soil

In the midst of the major soil degradation and erosion faced by tropical ecosystems, rehabilitated forests are being established to avoid the further deterioration of forest lands. In this context, cellulolytic, nitrogen-fixing (N-fixing), phosphate-solubilizing bacteria are very important functional groups in regulating the elemental cycle and plant nutrition, hence replenishing the nutrient content in forest soils. As is the case for other potential plant growth-promoting (PGP) rhizobacteria, these functional bacteria could have cross-functional abilities or beneficial traits that are essential for plants and can improve their growth. This study was conducted to isolate, identify, and characterize selected PGP properties of these three functional groups of bacteria from tropical rehabilitated forest soils at Universiti Putra Malaysia Bintulu Sarawak Campus, Malaysia. The bacteria were isolated based on their colonial growth on respective functional media, identified using both molecular and selected biochemical properties, and were assessed for their functional quantitative activities as well as PGP properties based on seed germination tests and indole-3-acetic acid (IAA) production. Out of the 15 identified bacterial isolates that exhibited beneficial phenotypic traits, a third belong to the genus Burkholderia and a fifth to Stenotrophomonas sp., with both genera consisting of members from two different functional groups. The results of the experiments confirm the multiple PGP traits of some selected bacterial isolates based on their respective high functional activities, root and shoot lengths, and seedling vigor improvements when bacterized on mung bean seeds, as well as significant IAA production. The results of this study suggest that these functional bacterial strains could potentially be included in bio-fertilizer formulations for crop growth on acid soils.

Potential PGPR Properties of Cellulolytic, Nitrogen-Fixing, Phosphate-Solubilizing Bacteria in Rehabilitated Tropical Forest Soil

In the midst of the major soil degradation and erosion faced by tropical ecosystems, rehabilitated forests are being established to avoid the further deterioration of forest lands. In this context, cellulolytic, nitrogen-fixing (N-fixing), phosphate-solubilizing bacteria are very important functional groups in regulating the elemental cycle and plant nutrition, hence replenishing the nutrient content in forest soils. As is the case for other potential plant growth-promoting (PGP) rhizobacteria, these functional bacteria could have cross-functional abilities or beneficial traits that are essential for plants and can improve their growth. This study was conducted to isolate, identify, and characterize selected PGP properties of these three functional groups of bacteria from tropical rehabilitated forest soils at Universiti Putra Malaysia Bintulu Sarawak Campus, Malaysia. The bacteria were isolated based on their colonial growth on respective functional media, identified using both molecular and selected biochemical properties, and were assessed for their functional quantitative activities as well as PGP properties based on seed germination tests and indole-3-acetic acid (IAA) production. Out of the 15 identified bacterial isolates that exhibited beneficial phenotypic traits, a third belong to the genus Burkholderia and a fifth to Stenotrophomonas sp., with both genera consisting of members from two different functional groups. The results of the experiments confirm the multiple PGP traits of some selected bacterial isolates based on their respective high functional activities, root and shoot lengths, and seedling vigor improvements when bacterized on mung bean seeds, as well as significant IAA production. The results of this study suggest that these functional bacterial strains could potentially be included in bio-fertilizer formulations for crop growth on acid soils.

Diazotroph Diversity and Nitrogen Fixation in Summer Active Perennial Grasses in a Mediterranean Region Agricultural Soil

Summer-growing perennial grasses such as Panicum coloratum L. cv. Bambatsi (Bambatsi panic), Chloris gayana Kunth cv. Katambora (Rhodes grass) and Digitaria eriantha Steud. cv. Premier (Premier digit grass) growing in the poor fertility sandy soils in the Mediterranean regions of southern Australia and western Australia mainly depend upon soil N and biological N inputs through diazotrophic (free living or associative) N fixation. We investigated the community composition and diversity (nifH-amplicon sequencing), abundance (qPCR) and functional capacity (15N incubation assay) of the endophytic diazotrophic community in the below and above ground plant parts of field grown and unfertilized grasses. Results showed a diverse and abundant diazotrophic community inside plant both above and below-ground and there was a distinct diazotrophic assemblage in the different plant parts in all the three grasses. There was a limited difference in the diversity between leaves, stems and roots except that Panicum grass roots harbored greater species richness. Nitrogen fixation potentials ranged between 0.24 and 5.9 mg N kg-1 day-1 and N fixation capacity was found in both the above and below ground plant parts. Results confirmed previous reports of plant species-based variation and that Alpha-Proteobacteria were the dominant group of nifH-harboring taxa both in the belowground and aboveground parts of the three grass species. Results also showed a well-structured nifH-harboring community in all plant parts, an example for a functional endophytic community. Overall, the variation in the number and identity of module hubs and connectors among the different plant parts suggests that co-occurrence patterns within the nifH-harboring community specific to individual compartments and local environments of the niches within each plant part may dictate the overall composition of diazotrophs within a plant.

Purple corn-associated rhizobacteria with potential for plant growth promotion

AIMS

Purple corn (Zea mays var. purple amylaceum) is a native variety of the Peruvian Andes, cultivated at 3000 m since the pre-Inca times without N fertilization. We aimed to isolate and identify native plant growth-promoting rhizobacteria (PGPR) for future microbial-based inoculants.

METHODS AND RESULTS

Eighteen strains were isolated from the rhizosphere of purple corn plants grown without N fertilization in Ayacucho (Peru). The 16S rRNA gene clustered the 18 strains into nine groups that contained species of Bacillus, Stenotrophomonas, Achromobacter, Paenibacillus, Pseudomonas and Lysinibacillus. A representative strain from each group was selected and assayed for N₂ fixation, phosphate solubilization, indole acetic and siderophore production, 1-aminocyclopropane-1-carboxylic acid deaminase activity and biocontrol abilities. Inoculation of purple corn plants with single and combined strains selected after a principal component analysis caused significant increases in root and shoot dry weight, total C and N contents of the plants.

CONCLUSIONS

PGPRs can support growth and crop production of purple corn in the Peruvian Andes and constitute the base for microbial-based inoculants.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study enlarges our knowledge on plant-microbial interactions in high altitude mountains and provides new applications for PGPR inoculation in purple amylaceum corn, which is part of the staple diet for the native Quechua communities.

The Endophytic Symbiont-Pseudomonas aeruginosa Stimulates the Antioxidant Activity and Growth of Achyranthes aspera L

A plant growth promoting bacterial endophyte designated as AL2-14B isolated from the leaves of Achyranthes aspera L. was identified as Pseudomonas aeruginosa based on its phenotypic and physiological features, and 16S rRNA gene sequence analysis. AL2-14B had plant growth stimulating attributes including siderophore and indole acetic acid release, inorganic phosphate solubilization, along with nitrogenase, ammonification, and protease activities. It also exhibited antifungal property against Rhizoctonia solani. The plantlets grown in germ-free condition were inoculated with AL2-14B and studied for the colonization of endophyte. Significant increase in population of AL2-14B between 3rd and 5th days after inoculation was recorded. The treatment of plants with endophytic P. aeruginosa AL2-14B increased nitrogen, phosphorus, potassium (NPK) contents in plant by 3.8, 12.59, and 19.15%, respectively. Significant enhancement of shoot and root length, dry leaf, dry shoot and dry root weight, and leaf surface area as compared to control (P < 0.05) was recorded in AL2-14B inoculated plants. The antioxidant activities increased in plants grown in germ-free conditions and inoculated with AL2-14B. The present study emphasizes on the role of diazotrophic endophyte P. aeruginosa AL2-14B in stimulating growth of A. aspera L. and improvement of its medicinal properties. Significant increase in growth and antioxidant content of P. aeruginosa AL2-14B treated plants suggests the possibility of an economical and eco-friendly mean of achieving antioxidants rich, healthier A. aspera plants.

Taxonomy and systematics of plant probiotic bacteria in the genomic era

Recent decades have predicted significant changes within our concept of plant endophytes, from only a small number specific microorganisms being able to colonize plant tissues, to whole communities that live and interact with their hosts and each other. Many of these microorganisms are responsible for health status of the plant, and have become known in recent years as plant probiotics. Contrary to human probiotics, they belong to many different phyla and have usually had each genus analysed independently, which has resulted in lack of a complete taxonomic analysis as a group. This review scrutinizes the plant probiotic concept, and the taxonomic status of plant probiotic bacteria, based on both traditional and more recent approaches. Phylogenomic studies and genes with implications in plant-beneficial effects are discussed. This report covers some representative probiotic bacteria of the phylum Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes, but also includes minor representatives and less studied groups within these phyla which have been identified as plant probiotics.

Molecular characterization and amplified ribosomal DNA restriction analysis of entomopathogenic bacteria associated with Rhabditis (Oscheius) spp

Bacterial strains associated with entomopathogenic nematodes (EPNs) Rhabditis (Oscheius) spp. were isolated from infected cadavers of Galleria mellonella. The obtained 18 isolates were subdivided into nine phylogenetically different genera based on comparative sequence analysis of their 16S rRNA genes. The isolates were affiliated to three different class namely γ-proteobacteria (Enterobacter, Proteus, Providencia, Pseudomonas, Stenotrophomonas), β-proteobacteria (Alcaligenes) and Bacilli (Bacillus, Enterococcus, Lysinibacillus). It was observed that Gram-positive strains (Bacilli) were more frequently associated with the EPN, whereas Gram-negative isolates were affiliated to six different genera with more genotypic diversity. Subsequently, all bacterial isolates used in this study were analyzed by amplified ribosomal DNA restriction analysis (ARDRA). Eight restriction endonucleases (CfoI, HinfI, RsaI, DdeI, Sau3AI, AluI, HaeIII, and MspI) were examined and a total of 15 different genotypes were obtained, forming two heterogenous main clusters after analysis by un-weighted pair-group method using arithmetic averages.

Search for endophytic diazotrophs in barley seeds

Eight endophytic isolates assigned to Pseudomonas, Azospirillum, and Bacillus genera according to pheno-genotypic features were retrieved from barley seeds under selective pressure for nitrogen-fixers. Genetic relationships among related isolates were investigated through RAPD. Six isolates displayed nitrogen-fixing ability, while all could biosynthesize indolacetic acid in vitro and showed no antibiosis effects against Azospirillum brasilense Az39, a recognized PGPR.

Morphological, biochemical and molecular characterization of twelve nitrogen-fixing bacteria and their response to various zinc concentration

BACKGROUND

Zinc is an essential micronutrient used in the form of zinc sulfate in fertilizers in the agriculture production system. Nitrogen-fixing microorganisms are also of considerable value in promoting soil fertility.

OBJECTIVES

This study aimed to investigate the degree of sensitivity to varying concentrations of zinc, in the form of ZnSO4, in different strains of Azotobacter chroococcum in a laboratory environment.

MATERIALS AND METHODS

To isolate A. chroococcum strains, soil samples were collected from wheat, corn and asparagus rhizospheres and cultured in media lacking nitrogen at 30˚C for 48 hours. Strains were identified based on morphological and biochemical characteristics. The presence of the nitrogenase enzyme system was confirmed by testing for the presence of the nifH gene using PCR analysis. The minimum inhibitory concentration (MIC) and optimal zinc concentration for the growth of each strain was determined.

RESULTS

A total of 12 bacterial strains were isolated from six different soil samples. A. chroococcum strains were morphologically and biochemically characterized. The presence of the nifH gene was confirmed in all the strains. MIC and the optimal zinc concentration for bacterial growth were 50 ppm and 20 ppm, respectively.

CONCLUSIONS

It was concluded that increasing the concentration of zinc in the agricultural soil is harmful to beneficial microorganisms and reduces the soil fertility. A 20-ppm zinc concentration in soil is suggested to be optimal.

Isolation and characterization of plant growth promoting traits of a rhizobacteria: Pantoea agglomerans lma2

The use of microbial technology in agriculture is expanding quickly with the identification of new bacterial strains which are more effective in promoting the growth of plants. The rhizobacteria that promote the growth of plants can have a positive effect on the productivity of crops especially when subjected to salt stress. A nitrogen-fixing bacterium was isolated from the wheat rhizosphere of an arid region. The strain was identified on the basis of tests API20E and 16S rRNA sequencing, as Pantoea agglomerans lma2. This strain degraded several carbon sources: sugars (fructose, ribose, dextrin, salicin...), lipids (lecithin, tributyrin and tween 80), proteins (gelatin, casein), grew on KCN and could grow from pH 4 to 8 and had an optimum at pH 7. The growth temperature showed a maximum at 30 degrees C and the bacteria could tolerate from 4 to 41 degrees C and the growth rate was higher when the NaCl concentration was between 100 and 300 mM. The performance of activities enhancing the growth of plants of P. agglomerans lma2 was significantly better in the presence of salt. Rates of Indole Acetic Acid (IAA), siderophores production and solubilization of phosphate increased between 100 and 400 mM NaCl compared to the control without salt. The maximum values were saved to 300 mM for the production of siderophores (18.32%) and solubilization of phosphate (1061.49 microg mL(-1)) and 100 mM for the production of IAA (161 microg mL(-1)). A significant correlation existed between these three activities. These results showed that P. agglomerans lma2 with its Plant Growth Promoting Rhizobacteria (PGPR) and halophilic properties could constitute a good fertilizer in arid and saline zone.

Microbes - friends and foes of sugarcane

Sugarcane is an important cash crop for many countries because it is a major source of several products including sugar and bioethanol. To obtain maximum yields there is a need to apply large quantities of chemical fertilizers.Worldwide yields are also severely affected by more than sixty diseases, mostly caused by fungi but viruses, phytoplasmas, nematodes and other pests can also damage this crop. For most of these diseases, chemical control is not available and breeders are struggling with the development of pest resistant varieties. Many members of the grass family Poaceae establish associations with beneficial microbes which promote their growth by direct and indirect mechanisms. They can be used as means to reduce the need for chemical fertilizer and to minimize the impacts of pathogen invasion. This review highlights the diversity of the microbes associated with sugarcane and the role of beneficial microbes for growth promotion and biocontrol. More extensive use of beneficial microbes will help the sugarcane grower not only to reduce the use of chemical fertilizers but also minimize the disease. In this paper, a brief description of both the non-pathogenic and pathogenic microbes associated with sugarcane is provided. Future prospects for the expanded use of beneficial microbes for sugarcane are also discussed and detailed herein.

Genetic diversity of endophytic diazotrophs of the wild rice, Oryza alta and identification of the new diazotroph, Acinetobacter oryzae sp. nov

Thirty-three endophytic diazotrophs were isolated from surface-sterilized leaves, stem, and roots of wild rice Oryza alta. The SDS-PAGE profile of total protein and insertion sequence-based polymerase chain reaction (IS-PCR) fingerprinting grouped the isolates into four clusters (I-IV). The 16S rRNA gene sequence homology of the representative strains B21, B31, B1, and B23 of clusters I, II, III, and IV were assigned to Pseudomonas oleovorans (99.2% similarity), Burkholderia fungorum (99.4% similarity), Enterobacter cloacae (98.9% similarity), and Acinetobacter johnsonii (98.4% similarity), respectively. The results showed wide genetic diversity of the putative diazotrophic strains of the wild rice, O. alta, and the strains of cluster IV are the first report of nitrogen-fixing Acinetobacter species. The cell size, phenotypic characters, total protein profile, genomic DNA fingerprinting, DNA-DNA hybridization, and antibiotic resistance differentiated strain B23(T) from its closest relatives A. johnsonii LMG999(T) and Acinetobacter haemolyticus LMG996(T). The DNA-DNA hybridization also distinguished the strain B23(T) from the closely related Acinetobacter species. Based on these data, a novel species, Acinetobacter oryzae sp. nov., and strain B23(T) (=LMG25575(T) = CGMCC1.10689(T)) as the type strain were proposed.

Screening for endophytic nitrogen-fixing bacteria in Brazilian sugar cane varieties used in organic farming and description of Stenotrophomonas pavanii sp. nov

A Gram-negative, rod-shaped, non-spore-forming and nitrogen-fixing bacterium, designated ICB 89(T), was isolated from stems of a Brazilian sugar cane variety widely used in organic farming. 16S rRNA gene sequence analysis revealed that strain ICB 89(T) belonged to the genus Stenotrophomonas and was most closely related to Stenotrophomonas maltophilia LMG 958(T), Stenotrophomonas rhizophila LMG 22075(T), Stenotrophomonas nitritireducens L2(T), [Pseudomonas] geniculata ATCC 19374(T), [Pseudomonas] hibiscicola ATCC 19867(T) and [Pseudomonas] beteli ATCC 19861(T). DNA-DNA hybridization together with chemotaxonomic data and biochemical characteristics allowed the differentiation of strain ICB 89(T) from its nearest phylogenetic neighbours. Therefore, strain ICB 89(T) represents a novel species, for which the name Stenotrophomonas pavanii sp. nov. is proposed. The type strain is ICB 89(T) ( = CBMAI 564(T)  = LMG 25348(T)).

Cultivation of anaerobic and facultatively anaerobic bacteria from spacecraft-associated clean rooms

In the course of this biodiversity study, the cultivable microbial community of European spacecraft-associated clean rooms and the Herschel Space Observatory located therein were analyzed during routine assembly operations. Here, we focused on microorganisms capable of growing without oxygen. Anaerobes play a significant role in planetary protection considerations since extraterrestrial environments like Mars probably do not provide enough oxygen for fully aerobic microbial growth. A broad assortment of anaerobic media was used in our cultivation strategies, which focused on microorganisms with special metabolic skills. The majority of the isolated strains grew on anaerobic, complex, nutrient-rich media. Autotrophic microorganisms or microbes capable of fixing nitrogen were also cultivated. A broad range of facultatively anaerobic bacteria was detected during this study and also, for the first time, some strictly anaerobic bacteria (Clostridium and Propionibacterium) were isolated from spacecraft-associated clean rooms. The multiassay cultivation approach was the basis for the detection of several bacteria that had not been cultivated from these special environments before and also led to the discovery of two novel microbial species of Pseudomonas and Paenibacillus.