A super sandstorm altered the abundance and composition of airborne bacteria in Beijing

Sandstorm, which injects generous newly emerging microbes into the atmosphere covering cities, adversely affects the air quality in built environments. However, few studies have examined the change of airborne bacteria during severe sandstorm events. In this work, we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia on March 15th, 2021, which affected large areas of China and Mongolia. The characteristics of the sandstorm were compared with those of the subsequent clean and haze days. The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction (qPCR) and high-throughput sequencing technology. During the sandstorm, the particulate matter (PM) concentration and bacterial richness were extremely high (PM2.5: 207 µg/m3; PM10: 1630 µg/m3; 5700 amplicon sequence variants/m3). In addition, the sandstorm brought 10 pathogenic bacterial genera to the atmosphere, posing a grave hazard to human health. As the sandstorm subsided, small bioaerosols (0.65-1.1 µm) with a similar bacterial community remained suspended in the atmosphere, bringing possible long-lasting health risks.

Generation of a high quality library of bioactive filamentous actinomycetes from extreme biomes using a culture-based bioprospecting strategy

Introduction

Filamentous actinomycetes, notably members of the genus Streptomyces, remain a rich source of new specialized metabolites, especially antibiotics. In addition, they are also a valuable source of anticancer and biocontrol agents, biofertilizers, enzymes, immunosuppressive drugs and other biologically active compounds. The new natural products needed for such purposes are now being sought from extreme habitats where harsh environmental conditions select for novel strains with distinctive features, notably an ability to produce specialized metabolites of biotechnological value.

Methods

A culture-based bioprospecting strategy was used to isolate and screen filamentous actinomycetes from three poorly studied extreme biomes. Actinomycetes representing different colony types growing on selective media inoculated with environmental suspensions prepared from high-altitude, hyper-arid Atacama Desert soils, a saline soil from India and from a Polish pine forest soil were assigned to taxonomically predictive groups based on characteristic pigments formed on oatmeal agar. One hundred and fifteen representatives of the colour-groups were identified based on 16S rRNA gene sequences to determine whether they belonged to validly named or to putatively novel species. The antimicrobial activity of these isolates was determined using a standard plate assay. They were also tested for their capacity to produce hydrolytic enzymes and compounds known to promote plant growth while representative strains from the pine forest sites were examined to determine their ability to inhibit the growth of fungal and oomycete plant pathogens.

Results

Comparative 16S rRNA gene sequencing analyses on isolates representing the colour-groups and their immediate phylogenetic neighbours showed that most belonged to either rare or novel species that belong to twelve genera. Representative isolates from the three extreme biomes showed different patterns of taxonomic diversity and characteristic bioactivity profiles. Many of the isolates produced bioactive compounds that inhibited the growth of one or more strains from a panel of nine wild strains in standard antimicrobial assays and are known to promote plant growth. Actinomycetes from the litter and mineral horizons of the pine forest, including acidotolerant and acidophilic strains belonging to the genera Actinacidiphila, Streptacidiphilus and Streptomyces, showed a remarkable ability to inhibit the growth of diverse fungal and oomycete plant pathogens.

Discussion

It can be concluded that selective isolation and characterization of dereplicated filamentous actinomyctes from several extreme biomes is a practical way of generating high quality actinomycete strain libraries for agricultural, industrial and medical biotechnology.

Genus Pseudonocardia: What we know about its biological properties, abilities and current application in biotechnology

The genus Pseudonocardia belongs to a group of Actinomycetes, and is a member of the family Pseudonocardiacea. The members of this genus are aerobic, Gram-positive, non-motile bacteria that are commonly found in soil, plant and environment. Although this genus has a low clinical significance; however, it has an important role in biotechnology due to the production of secondary metabolites, some of which have anti-bacterial, anti-fungal and anti-tumour effects. The use of phenotypic tests, such as gelatinase activity, starch hydrolysis, catalase and oxidase tests, as well as molecular methods, such as polymerase chain reaction, are necessary for Pseudonocardia identification at the genus and species levels.

Pseudonocardia tritici sp. nov., a novel actinomycete isolated from rhizosphere soil of wheat (Triticum aestivum L.)

An aerobic, non-motile, Gram-stain positive actinomycete, designated strain NEAU-YY211^T, was isolated from the rhizosphere soil of wheat (Triticum aestivum L.) collected from Zhumadian, Henan Province, mid-eastern China, and characterised taxonomically using a polyphasic approach. Comparative analysis of the 16S rRNA gene sequence indicated that strain NEAU-YY211^T belongs to the genus Pseudonocardia, showing high similarities with respect to Pseudonocardia ammonioxydans H9^T (99.1%) and Pseudonocardia antitumoralis SCSIO 01299^T (99.0%), respectively. The cell wall was found to contain meso-diaminopimelic acid and the whole cell sugars were identified as arabinose and galactose. The predominant menaquinone of strain NEAU-YY211^T was identified as MK-8(H₄) and the major fatty acids were identified as iso-C_16:0, C_17:1ω8c and iso-C_16:1. The phospholipid profile was found to consist of diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol and an unidentified phospholipid. The G+C content of the genomic DNA was determined to be 72.6 mol%. Levels of DNA-DNA relatedness with P. ammonioxydans JCM 12462^T and P. antitumoralis DSM 45322^T were 54.5 ± 3.5% and 49.8 ± 2.5% (mean ± SD), respectively. Based on phylogenetic analysis, phenotypic and genotypic data, it is concluded that the isolate can be distinguished from closely related type strains and thus represents a novel species of the genus Pseudonocardia, for which the name Pseudonocardia tritici sp. nov. is proposed. The type strain is NEAU-YY211^T (= DSM 106068^T = CGMCC 4.7474^T).

Pseudonocardia cypriaca sp. nov., Pseudonocardia salamisensis sp. nov., Pseudonocardia hierapolitana sp. nov. and Pseudonocardia kujensis sp. nov., isolated from soil

The taxonomic positions of four novel actinomycetes isolated from soil samples, designated KT2142T, PM2084T, K236T and A4038T, were established by using a polyphasic approach. The organisms had chemical and morphological features that were consistent with their classification in the genus Pseudonocardia. Whole-cell hydrolysates of the four strains contained meso-diaminopimelic acid and arabinose and galactose as the diagnostic sugars (cell-wall type IV). Their predominant menaquinone was found to be MK-8(H4). The major fatty acid was iso-C16:0. 16S rRNA gene sequence data supported the classification of the isolates in the genus Pseudonocardia and showed that they formed four distinct branches within the genus. DNA-DNA relatedness studies between the isolates and their phylogenetic neighbours showed that they belonged to distinct genomic species. The four isolates were readily distinguished from one another and from the type strains of species classified in the genus Pseudonocardia based on a combination of phenotypic and genotypic properties. In conclusion, it is proposed that the four isolates be classified in four novel species of the genus Pseudonocardia, for which the names Pseudonocardia cypriaca sp. nov. (type strain KT2142T=KCTC 29067T=DSM 45511T=NRRL B-24882T), Pseudonocardia hierapolitana sp. nov. (type strain PM2084T=KCTC 29068T=DSM 45671T=NRRL B-24879T), Pseudonocardia salamisensis sp. nov. (type strain K236T=KCTC 29100T=DSM 45717T) and Pseudonocardia kujensis sp. nov. (type strain A4038T=KCTC 29062T=DSM 45670T=NRRL B-24890T) are proposed.

Pseudonocardia hispaniensis sp. nov., a novel actinomycete isolated from industrial wastewater activated sludge

A novel actinomycete, designated PA3(T), was isolated from an oil refinery wastewater treatment plant, located in Palos de la Frontera, Huelva, Spain, and characterized taxonomically by using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate formed a distinct subclade in the Pseudonocardia tree together with Pseudonocardia asaccharolytica DSM 44247(T). The chemotaxonomic properties of the isolate, for example, the presence of MK-8 (H(4)) as the predominant menaquinone and iso-C(16:0) as the major fatty acid, are consistent with its classification in the genus Pseudonocardia. DNA:DNA pairing experiments between the isolate and the type strain of P. asaccharolytica DSM 44247(T) showed that they belonged to separate genomic species. The two strains were readily distinguished using a combination of phenotypic properties. Consequently, it is proposed that isolate PA3(T) represents a novel species for which the name Pseudonocardia hispaniensis sp. nov. is proposed. The type strain is PA3(T) (= CCM 8391(T) = CECT 8030(T)).

Pseudonocardia kunmingensis sp. nov., an actinobacterium isolated from surface-sterilized roots of Artemisia annua L

A Gram-positive, aerobic, actinobacterial strain with rod-shaped spores, designated YIM 63158(T), was isolated from the surface-sterilized roots of Artemisia annua L. collected from Yunnan province, south-west China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM 63158(T) belonged to the genus Pseudonocardia. The closest neighbours were 'Pseudonocardia sichuanensis' KLBMP 1115 (99.9 % 16S rRNA gene sequence similarity), Pseudonocardia adelaidensis EUM 221(T) (99.1 %) and Pseudonocardia zijingensis DSM 44774(T) (98.8 %); sequence similarities to other members of the genus Pseudonocardia ranged from 98.6 to 94.4 %. The chemotaxonomic characteristics, such as the cell-wall diaminopimelic acid, whole-cell sugars, fatty acid components and major menaquinones, suggested that the isolate belonged to the genus Pseudonocardia. The G+C content of the genomic DNA was 73.3 mol%. On the basis of physiological, biochemical and chemotaxonomic data, including low DNA-DNA relatedness between the isolate and other members of the genus Pseudonocardia, it is proposed that strain YIM 63158(T) represents a novel species in this genus, with the name Pseudonocardia kunmingensis sp. nov. The type strain is YIM 63158(T) ( = DSM 45301(T)  = CCTCC AA 208078(T)). [corrected].