Ribosomally derived lipopeptides containing distinct fatty acyl moieties

Lipopeptides represent a large group of microbial natural products that include important antibacterial and antifungal drugs and some of the most-powerful known biosurfactants. The vast majority of lipopeptides comprise cyclic peptide backbones N-terminally equipped with various fatty acyl moieties. The known compounds of this type are biosynthesized by nonribosomal peptide synthetases, giant enzyme complexes that assemble their products in a non–gene-encoded manner. Here, we report the genome-guided discovery of ribosomally derived, fatty-acylated lipopeptides, termed selidamides. Heterologous reconstitution of three pathways, two from cyanobacteria and one from an arctic, ocean-derived alphaproteobacterium, allowed structural characterization of the probable natural products and suggest that selidamides are widespread over various bacterial phyla. The identified representatives feature cyclic peptide moieties and fatty acyl units attached to (hydroxy)ornithine or lysine side chains by maturases of the GCN5-related N-acetyltransferase superfamily. In contrast to nonribosomal lipopeptides that are usually produced as congener mixtures, the three selidamides are selectively fatty acylated with C10, C12, or C16 fatty acids, respectively. These results highlight the ability of ribosomal pathways to emulate products with diverse, nonribosomal-like features and add to the biocatalytic toolbox for peptide drug improvement and targeted discovery.

Filtered mud improves sugarcane growth and modifies the functional abundance and structure of soil microbial populations

Background Exploring high-quality organic amendments has been a focus of sustainable agriculture. Filtered mud (FM), a sugar factory waste derived from sugarcane stems, could be an alternative organic amendment for sugarcane production. However, the effects of its application proportions on soil fertility, nutrient cycling, structure of soil bacterial and fungal communities, and the growth of sugarcane in clay-loam soils remain unexplored. Methods Three application proportions of FM: (FM1-(FM: Soil at 1:4), FM2-(FM: Soil at 2:3), and FM3-(FM: Soil at 3:2)) were evaluated on sugarcane growth and soil nutrient cycling. High throughput sequencing was also employed to explore soil microbial dynamics. Results We observed that FM generally increased the soil’s nutritional properties while improving NO3− retention compared to the control, resulting in increased growth parameters of sugarcane. Specifically, FM1 increased the concentration of NH4+−N, the N fraction preferably taken up by sugarcane, which was associated with an increase in the plant height, and more improved growth properties, among other treatments. An increase in the proportion of FM also increased the activity of soil nutrient cycling enzymes; urease, phosphatase, and β-glucosidase. High throughput sequencing revealed that FM reduced the diversity of soil bacteria while having insignificant effects on fungal diversity. Although increasing FM rates reduced the relative abundance of the phyla Proteobacteria, its class members, the Gammaproteobacteria and Betaproteobacteria containing some N-cycling related genera, were stimulated. Also, FM stimulated the abundance of beneficial and lignocellulose degrading organisms. These included the bacterial phyla Actinobacteria, Bacteroidetes, Acidobacteria, Chloroflexi, and the fungal phylum Ascomycota. The distribution of the soil microbial community under FM rates was regulated by the changes in soil pH and the availability of soil nutrients. Since FM1 showed more promise in improving the growth properties of sugarcane, it could be more economical and sustainable for sugarcane production in clay-loam soils.

First Report of Fecal Microflora of Wild Bar-Headed Goose in Tibet Plateau

The bar-headed goose (Anser indicus) has two black spots on its head. It is considered an important bird in China. It breeds in plateau lakes, especially saltwater lakes, and swamp areas. However, the intestinal flora of wild bar-headed geese in the Tibet Autonomous Region is currently not known. In this study, 16S rDNA sequencing was performed on the intestinal microbes of wild bar-headed geese. A total of 513,505 reads of raw data were obtained, and the results analyzed the average number of 128,376 ± 2,392 reads per sample. The microbiota of all samples consists of 10 main bacterial phyla, including Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, Patescibacteria, Deferribacteres, Planctomy-cetes, Fusobacteria, and Tenericutes. The results indicated that Firmicutes (67.34%) was the predominant phylum, followed by Proteobacteria (29.03%) and Cyanobacteria (1.97%). In our research, we identified the intestinal flora of the wild bar-headed goose, which provides valuable information for further research on the gene function of the bar-headed goose and the intestinal flora of wild animals. These findings are also useful and valuable for genetic and high-altitude research in the Tibet Autonomous Region.

An NMR fingerprint matching approach for the identification and structural re-evaluation of Pseudomonas lipopeptides.

Cyclic lipopeptides (CLiPs) are secondary metabolites secreted by a range of bacterial phyla. CLiPs display diverse structural variations in terms of the number of the amino acid residues, macrocycle size, amino acid identity and stereochemistry (e.g. D- vs. L-amino acids). Reports detailing the discovery of novel or already characterized CLiPs from new sources appear regularly in literature. However, in some cases, the lack of characterization detail threatens to cause considerable confusion, especially if configurational heterogeneity is present for one or more amino acids. The NMR fingerprint matching approach introduced in this work exploits the fact that the 1H and 13C NMR chemical shift fingerprint is sufficiently sensitive to differentiate the diastereomers of a particular CLiP even when they only differ in a single D/L configuration. This provides a means for a fast screening to determine whether an extracted CLiP has been reported before, by simply comparing the fingerprint of a novel CLiP with that of a reference CLiP. Even when the stereochemistry of a particular reference CLiP is unknown, the NMR fingerprint approach still allows to verify whether a CLiP from a novel source is identical to the reference. To facilitate this, we have made a publicly available knowledge base at https://www.rhizoclip.be, where we present an overview of published NMR fingerprint data of characterized CLiPs, together with literature data on the originally determined structures. The latter includes a description of the CLiPs original description, molecular mass, three dimensional structures (if available), and a summary of published antimicrobial activities. Moreover, a detailed protocol will be made available for researchers that wish to record NMR data of their newly extracted lipopeptides to compare them to the publicly available reference data.

Distinct soil bacterial patterns along narrow and broad elevational gradients in the grassland of Mt. Tianshan, China

Bacteria are essential regulators of soil biogeochemical cycles. While several studies of bacterial elevational patterns have been performed in recent years, the drivers of these patterns remain incompletely understood. To clarify bacterial distribution patterns and diversity across narrow- and broad-scale elevational gradients, we collected soil samples from 22 sites in the grasslands of Mt. Tianshan in China along three elevational transects and the overall elevation transect: (1) 6 sites at elevations of 1047–1587 m, (2) 8 sites at 876–3070 m, and (3) 8 sites at 1602–2110 m. The bacterial community diversity across the overall elevation transects exhibited a hump-like pattern, whereas consistent patterns were not observed in the separate elevational transects. The bacterial community composition at the phylum level differed across the transects and elevation sites. The Actinobacteria was the most abundant phylum overall (41.76%) but showed clear variations in the different transects. Furthermore, heatmap analyses revealed that both pH and mean annual temperature (MAT) were significantly (P < 0.05) correlated with bacterial community composition as well as the dominant bacterial phyla, classes, and genera. These findings provide an inclusive view of bacterial community structures in relation to the environmental factors of the different elevational patterns.

Bacterial and plankton communities in mariculture water sources: a case study in Nampu and Sembukan seawaters, Wonogiri, Indonesia

Seawaters in Indonesia, part of the tropical marine ecosystem, have great microbial and plankton diversity. Seawater is used as a water source for marine aquacultures, such as shrimp, milkfish, lobster, and mud crab. Sustainability of environmental resources for supporting aquaculture activities can be assessed by analyzing the actual conditions of the water source environment, including bacterial and plankton communities. However, the characteristics of bacteria and plankton communities in Indonesian seawaters have not been well documented. In this study, we investigated the bacterial and plankton communities in surface seawater from two coastal areas, i.e. Nampu and Sembukan, Wonogiri regency, Central Java, Indonesia. Bacterial diversity was analyzed using the Illumina-based high throughput sequencing with a primer set targeting the V3-V4 region of the bacterial 16S rRNA gene. Meanwhile, the plankton community (phytoplankton and zooplankton) was calculated and identified using a counting chamber method. Sequencing analysis revealed that the five dominant bacterial phyla in the two seawater samples were similar, consisting of Proteobacteria, Firmicutes, Actinobacteria, Bacteriodetes, and Cyanobacteria. Although the two sites are separated by several kilometres, the distribution of dominant bacterial phyla in both seawater samples is similar. Phytoplankton in Nampu and Sembukan were similarly dominated by Trichodesmium sp., Navicula sp., and Rhabdonema sp. Dominant zooplankton in the two sites were Euterpina, Nauplius, Oithona sp., Oncaea sp., Tigriopus sp., and Gastropoda larvae. The seawater in Nampu and Sembukan is suitable as a water source for aquaculture.

Taxonomic structure of tissue endophytic bacterial microbiome in clonal apple rootstock grown on sod-podzolic soils with variant properties

The taxonomic structure of tissue endophytic bacterial microbiome was comparatively studied in microplants (undifferentiated explant callus tissues, passage 25) and 5-year clonal apple rootstocks 57-490 and 54-118 cultured from corresponding tissues (passage 1) on sod-podzolic soils with variant granulometry, chemical, physical and physicochemical properties. Proteobacteria (91.6 %) predominated in vitro tissues among other endophytic bacterial phyla in rootstock 57-490, while Proteobacteria (52.5 %) and Firmicutes (47.4 %) — in rootstock 54-118. The endophytic Firmicutes ratio vs. in vitro tissues decreases (0.7-2.0 %) in roots and more severely (0-0.2 %) in leaves. Endophytic Actinobacteriota are revealed in 11.7 % in roots of the study rootstock in heavy loam soil, whilst in medium loam their ratio drops to 2.74.1 % in roots and 0.1-0.2 % in leaves. The phylogenetic diversity indices estimation for main endophytic bacterial phyla in apple rootstock tissue recovers their essentially lower diversity and evenness in culture endosphere (Shannon index 0.42-1.00) vs. open soil roots (1.34-2.08). The leaves Shannon index is typically low (0.06-0.13) indicating poor diversity and evenness of the main endophytic bacterial phyla.

Organic Carbon Mineralization and Bacterial Community of Active Layer Soils Response to Short-Term Warming in the Great Hing’an Mountains of Northeast China

As a buffer layer for the energy and water exchange between atmosphere and permafrost, the active layer is sensitive to climate warming. Changes in the thermal state in active layer can alter soil organic carbon (SOC) dynamics. It is critical to identify the response of soil microbial communities to warming to better predict the regional carbon cycle under the background of global warming. Here, the active layer soils collected from a wetland-forest ecotone in the continuous permafrost region of Northeastern China were incubated at 5 and 15°C for 45 days. High-throughput sequencing of the 16S rRNA gene was used to examine the response of bacterial community structure to experimental warming. A total of 4148 OTUs were identified, which followed the order 15°C &gt; 5°C &gt; pre-incubated. Incubation temperature, soil layer and their interaction have significant effects on bacterial alpha diversity (Chao index). Bacterial communities under different temperature were clearly distinguished. Chloroflexi, Actinobacteria, Proteobacteria, and Acidobacteria accounted for more than 80% of the community abundance at the phylum level. Warming decreased the relative abundance of Chloroflexi and Acidobacteria, while Actinobacteria and Proteobacteria exhibited increasing trend. At family level, the abundance of norank_o__norank_c__AD3 and Ktedonobacteraceae decreased significantly with the increase of temperature, while Micrococcaccac increased. In addition, the amount of SOC mineralization were positively correlated with the relative abundances of most bacterial phyla and SOC content. SOC content was positively correlated with the relative abundance of most bacterial phyla. Results indicate that the SOC content was the primary explanatory variable and driver of microbial regulation for SOC mineralization. Our results provide a new perspective for understanding the microbial mechanisms that accelerates SOC decomposition under warming conditions in the forest-wetland ecotone of permafrost region.

The Azurin Coding Gene: Origin and Phylogenetic Distribution

Azurin is a bacterial-derived cupredoxin, which is mainly involved in electron transport reactions. Interest in azurin protein has risen in recent years due to its anticancer activity and its possible applications in anticancer therapies. Nevertheless, the attention of the scientific community only focused on the azurin protein found in Pseudomonas aeruginosa (Proteobacteria, Gammaproteobacteria). In this work, we performed the first comprehensive screening of all the bacterial genomes available in online repositories to assess azurin distribution in the three domains of life. The Azurin coding gene was not detected in the domains Archaea and Eucarya, whereas it was detected in phyla other than Proteobacteria, such as Bacteroidetes, Verrucomicrobia and Chloroflexi, and a phylogenetic analysis of the retrieved sequences was performed. Observed patchy distribution and phylogenetic data suggest that once it appeared in the bacterial domain, the azurin coding gene was lost in several bacterial phyla and/or anciently horizontally transferred between different phyla, even though a vertical inheritance appeared to be the major force driving the transmission of this gene. Interestingly, a shared conserved domain has been found among azurin members of all the investigated phyla. This domain is already known in P. aeruginosa as p28 domain and its importance for azurin anticancer activity has been widely explored. These findings may open a new and intriguing perspective in deciphering the azurin anticancer mechanisms and to develop new tools for treating cancer diseases.

Animal soil food web complexity triggers shifts in microbial communities, including PAH degraders, but without clear effects on phenanthrene phytoremediation

The aim of this study was to determine whether the complexity of the animal soil food web (SFWC) is a significant factor influencing the soil microbial communities, the productivity of the willow, and the degradation rates of 100 mg kg-1 phenanthrene contamination. The SFWC treatment had eight levels: just the microbial community (BF), or the BF with nematodes (N), springtails (C), earthworms (E), CE, CN, EN, CEN. After eight weeks of growth, the height and biomass of willows were significantly affected by the SFWC, whereas the amount of phenanthrene degraded was not affected, reaching over 95% in all pots. SFWC affected the structure and the composition of the bacterial, archaeal and fungal communities, with significant effects of SFWC on the relative abundance of fungal genera such as Sphaerosporella, a known willow symbiont during phytoremediation, and bacterial phyla such as Actinobacteriota, containing many PAH degraders. These SFWC effects on microbial communities were not clearly reflected in the community structure and abundance of PAH degraders, even though some degraders related to the Actinobacteriota and the diversity of Gram-negative degraders were affected by the SFWC treatments. Overall, our results suggest that, under our experimental conditions, SFWC does not affect significantly willow phytoremediation outcomes.