Microbially influenced corrosion (MIC) may contribute significantly to overall corrosion risks, especially in the gas and petroleum industries. In this study, we isolated four Prolixibacter strains, which belong to the phylum Bacteroidetes, and examined their nitrate-respiration- and Fe0-corroding activities, together with two previously isolated Prolixibacter strains. Four of the six Prolixibacter strains reduced nitrate under anaerobic conditions, while the other two strains did not. The anaerobic growth of the four nitrate-reducing strains was enhanced by nitrate, which was not observed in the two nitrate-non-reducing strains. When the nitrate-reducing strains were grown anaerobically in the presence of Fe0 or carbon steel, the corrosion of the materials was enhanced by more than 20-fold compared to that in aseptic controls. This enhancement was not observed in cultures of the nitrate-non-reducing strains. The oxidation of Fe0 in the anaerobic cultures of nitrate-reducing strains occurred concomitantly with the reduction of nitrite. Since nitrite chemically oxidized Fe0 under anaerobic and aseptic conditions, the corrosion of Fe0- and carbon-steel by the nitrate-reducing Prolixibacter strains was deduced to be mainly enhanced via the biological reduction of nitrate to nitrite, followed by the chemical oxidation of Fe0 to Fe2+ and Fe3+ coupled to the reduction of nitrite.
As apex predators, pinnipeds are considered to be useful bioindicators of marine and coastal environments. Endemic to a small archipelago in the South Pacific, the Juan Fernandez fur seal (JFFS) is one of the less-studied members of the pinniped family Otariidae. This study aimed to characterize the fecal microbiome of the JFFS for the first time, in order to establish a baseline for future studies of host-microbial-environment interactions and monitoring programs. During two consecutive reproductive seasons, 57 fecal samples were collected from 7 different JFFS colonies within the Juan Fernandez Archipelago, Chile. Bacterial composition and abundance were characterized by sequencing the V4 region of the 16S rRNA gene. The overall microbiome composition was dominated by five phyla: Firmicutes (40 %), Fusobacteria (30 %), Bacteroidetes (22 %), Proteobacteria (6 %) and Actinobacteria (2 %). Alpha diversity was higher in Tierras Blancas. However, location was not found to be a dominant driver of microbial composition. Interestingly, the strongest signal in the data was a negative association between the genera Peptoclostridium and Fusobacterium, which explained 29.7 % of the total microbial composition variability between samples. The genus Peptoclostridium has not been reported in other pinniped studies and its role here is unclear, with interpretation challenging due to a lack of information regarding microbiome functionality in marine mammals. As a first insight into the JFFS fecal microbiome, these results contribute towards our understanding of the natural microbial diversity and composition in free-ranging pinnipeds.
The enormous complexity of the eukaryotic ribosome has been a real challenge in unlocking the mechanistic aspects of its amazing molecular function during mRNA translation and many non-canonical activities of ribosomal proteins in eukaryotic cells. While exploring the uncanny nature of ribosomal P proteins in malaria parasites Plasmodium falciparum, the 60S stalk ribosomal P2 protein has been shown to get exported to the infected erythrocyte (IE) surface as an SDS resistant oligomer during the early to mid trophozoite stage. Inhibiting IE surface P2 either by monoclonal antibody or through genetic knockdown resulted in nuclear division arrest of the parasite. This very strange and serendipitous finding has led us to explore more about un-canonical cell biology and structural involvement of P2 protein in Plasmodium in the search for a novel biochemical role during parasite propagation in the human host.
Naphthenic acids (NAs) are carboxylic acids with the formula (CnH2n+ZO2) and are the toxic, persistent constituents of oil sands process-affected waters (OSPW), produced during oil sands extraction. Currently, the proteins and mechanisms involved in NA biodegradation are unknown. Using LC-MS/MS shotgun proteomics, we identified proteins overexpressed during the growth of Pseudomonas fluorescens Pf5 on a model NA (4-n-butylphenyl)-4-butanoic acid (n-BPBA) and commercial NA mixture (Acros). By day 11, >95% of n-BPBA was degraded. With Acros, a 17% reduction in intensity occurred with 10-18 carbon compounds of the Z family -2 to -14 (major NA species in this mixture). A total of 554 proteins (n-BPBA) and 631 proteins (Acros) were overexpressed during growth on NAs; including several transporters (e.g. ABC transporters), suggesting a cellular protective response from NA toxicity. Several proteins associated with fatty acid, lipid and amino acid metabolism were also overexpressed; including acyl-CoA dehydrogenase and acyl-CoA thioesterase II, which catalyze part of the fatty acid beta-oxidation pathway. Indeed, multiple enzymes involved in the fatty acid oxidation pathway were upregulated. Given the presumed structural similarity between alkyl-carboxylic acid side chains and fatty acids, we postulate that P. fluorescens Pf-5 was using existing fatty acid catabolic pathways (among others) during NA degradation.
We report here the complete genome sequence of the Rhizobium rhizogenes (formerly Agrobacterium rhizogenes) strain LBA9402 (NCPPB1855rifR), a pathogenic strain causing hairy root disease. In order to assemble a complete genome we obtained short-reads from Illumina sequencing as well as long-reads from Oxford Nanopore Technology sequencing. The genome consists of a 3,958,212 bp chromosome, a 2,005,144 bp chromid (secondary chromosome) and a 252,168 bp Ri plasmid (pRi1855), respectively. The primary chromosome was very similar to that of the avirulent biocontrol strain K84, but the chromid showed a 724 kbp deletion accompanied by a large 1.8 Mbp inversion revealing the dynamic nature of these secondary chromosomes. The sequence of the agropine Ri plasmid was compared to other types of Ri and Ti plasmids. Thus we identified the genes responsible for agropine catabolism, but also a unique segment adjacent to the TL-region that has the signature of a new opine catabolic gene cluster including the three genes that together encode an opine dehydrogenase. Our sequence analysis also revealed a novel gene at the very right end of the TL-DNA, which is unique for the agropine Ri plasmid. The protein encoded by this gene was most related to the succinamopine synthases of chrysopine and agropine Ti plasmids and thus may be involved in synthesis of the unknown opine that can be degraded by the adjacent catabolic cluster. The available sequence will facilitate the use of R. rhizogenes and especially LBA9402 in both the laboratory and for biotechnological purposes.
The basal zone of glaciers is characterised by physicochemical properties that are distinct from firnified ice because of strong interactions with underlying substrate. Basal ice ecology and the roles that the microbiota play in biogeochemical cycling, weathering, and proglacial soil formation, remains poorly known. We report bacterial diversity and potential ecological roles at three temperate Icelandic glaciers. We sampled three physically distinct basal ice facies (stratified, dispersed, debris bands) and found biological similarities and differences between them; basal ice character is therefore an important sampling consideration in future studies. High abundance of silicates and Fe-containing minerals could sustain the basal ice ecosystem, in which chemolithotrophic bacteria (~23%), especially Fe-oxidisers and hydrogenotrophs, can fix C, which can be utilised by heterotrophs. Methanogenic-affiliated detected sequences showed that silicate comminution-derived hydrogen can also be utilised for methanogenesis. Metabolism predicted by 16S rRNA diversity revealed that methane metabolism and C-fixation are the most common pathways, indicating the importance of these metabolic routes. Carbon concentrations were low compared to other ecosystems, but we report the highest carbon concentration in basal ice to date. Carbon release from melting basal ice may play an important role in promoting pioneering communities establishment and soil development in deglaciating forelands.
In the microbiological diagnosis of bloodstream infections (BSI), blood culture (BC) is considered the gold standard test despite its limitations such as low sensitivity and slow turnaround time. A new FDA-cleared and CE-marked platform utilizing magnetic resonance to detect amplified DNA of the six most common and/or problematic BSI pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli) is available and may shorten the time to diagnosis and potentially improve antimicrobial utilization. Whole blood samples from hospitalized patients with clinical signs of sepsis were analyzed using the T2Bacteria Panel (T2Biosystems) and compared to simultaneously collected BC. Discrepant results were evaluated based on clinical infection criteria, combining supporting culture results and the opinion of treating physicians. A total of 55 samples from 53 patients were evaluated. The sensitivity and specificity of the T2Bacteria panel was 94% (16 out of 17 detections of T2Bacteria-targeted organisms) and 100%, respectively, with 36.4% (8 of 22) causes of BSI detected only by this method. The T2Bacteria Panel detected pathogens on average 55 hours faster than standard BC. In our study, 9 of 15 patients with positive T2Bacteria Panel results received early-targeted antibiotic therapy, and/or their antimicrobial treatment was modified based on T2Bacteria Panel findings. Given the high reliability, faster time to detection, and easy workflow, the technique qualifies as a point of care testing approach.
Bromus tectorum (cheatgrass) is an invasive annual grass that has colonized large portions of the Intermountain Western United States. Cheatgrass stand failures have been observed throughout the invaded region, the cause of which may be related to the presence of several species of pathogenic fungi in the soil or surface litter. In this metagenomic study, we compared the fungal communities between sites that have and have not experienced stand failure. Samples were taken from the soil and surface litter near Winnemucca, Nevada and in Skull Valley, Utah. Our results show distinct fungal communities associated with stand failure based on both geography and sample type. In both the Winnemucca and Skull Valley surface litter, there was an elevated abundance of the endophyte Ramimonilia apicalis in samples that had experienced a stand failure. Winnemucca surface litter stand failure samples had increased abundance of a potential pathogen in the genus Comoclathris. Skull Valley surface litter stand failure samples had increased abundance of the known cheatgrass pathogen Clarireedia capillus-albis while the soils had increased abundance of potential pathogens in the genera Olpidium and Monosporascus.
Carotenoids are widely used in functional foods, cosmetics, and health supplements, and their importance and scope of use are continuously expanding. Here, we characterised carotenoid biosynthetic genes of the plant-pathogenic bacterium Pantoea ananatis, which carries a carotenoid biosynthetic gene cluster (including crtE, X, Y, I, B, and Z) on a plasmid. Reverse transcription–polymerase chain reaction (RT-PCR) analysis revealed that the crtEXYIB gene cluster is transcribed as a single transcript and crtZ is independently transcribed in the opposite direction. Using splicing by overlap extension with polymerase chain reaction (SOE by PCR) based on asymmetric amplification, we reassembled crtE–B, crtE–B–I, and crtE–B–I–Y. High-performance liquid chromatography confirmed that Escherichia coli expressing the reassembled crtE–B, crtE–B–I, and crtE–B–I–Y operons produced phytoene, lycopene, and β-carotene, respectively. We found that the carotenoids conferred tolerance to UV radiation and toxoflavin. Pantoea ananatis shares rice environments with the toxoflavin producer Burkholderia glumae and is considered to be the first reported example of producing and using carotenoids to withstand toxoflavin. We confirmed that the carotenoid production of P. ananatis is dependent on RpoS, which is positively regulated by Hfq/ArcZ and negatively regulated by ClpP, similar to an important regulatory network of E. coli (HfqArcZ → RpoS Ͱ ClpXP). We also demonstrated that Hfq-controlled quorum signalling de-represses EanR to activate RpoS, thereby initiating carotenoid production. Survival genes such as those responsible for the production of carotenoids of the plant-pathogenic P. ananatis must be expressed in a timely manner to overcome stressful environments and compete with other microorganisms. This mechanism is likely maintained by a brake with excellent performance, such as EanR.
The ability of S. aureus to infect bone and osteoblasts is correlated to its incredible virulence armamentarium that can mediate the invasion/internalization process, cytotoxicity, membrane damage and intracellular persistence. We comparatively analyzed the interaction, persistence and modulation of expression of selected genes as well as cell viability in an ex-vivo model using human MG-63 osteoblasts of two previously studied and well-characterized S. aureus clinical strains belonging to ST239-SCCmecIII-t037 and ST228-SCCmecI-t041 clones at 3h and 24h post-infection (p.i). ATCC12598 was used as a control strain. Using Imaging Flow Cytometry analysis, we found that strains differently invaded osteoblasts after 3h and 24h: ATCC12598 internalized in 70% and 50% of cells, ST239-SCCmecIII in 50% and 45% and ST228-SCCmecI in 30% and 20%, respectively. ST239-III, during the infection period, exerted a significative cytotoxic activity due to the over-expression of hla and psmA and the increased expression of the genes involved in adhesion, probably due to the release and re-entry of bacteria inside MG-63 at 24h p.i. The lower invasiveness of ST228-I was also correlated with the non-cytotoxic activity inside osteoblasts. This clone was not able to activate a sufficient cellular reaction and succumbed in-side the MG-63 cells.
To survive within complex environmental niches, including the human host, bacteria have evolved intricate inter-species communities driven by competition for limited nutrients, cooperation via complementary metabolic proficiencies, and establishment of homeostatic relationships with the host immune system. Such complex, interdependent relationships have hampered attempts to culture many bacterial strains in research settings, where standard readout of co-culture experiments are usually limited to the relative abundance of each species. Here, we utilize a microfluidic-based co-culture system to characterize dynamic interactions between multiple oral bacterial isolates. Using time-lapse imaging, we define species-specific effects on spatial community relationships during co-culture of Streptococcus species and Staphylococcus aureus with Actinomyces species. Co-culture of Streptococcus cristatus or S. salivarius in nanoliter compartments with Actinomyces graevenitzii revealed localized exclusion of Streptococcus and Staphylococcus from media immediately surrounding A. graevenitzii micro colonies. This community structure did not occur with S. mitis or S. oralis strains, or in co-cultures containing other Actinomycetaceae species such as S. odontolyticus or A. naeslundii. Moreover, fewer neutrophils were attracted to compartments containing both A. graevenitzii and Staphylococcus aureus than to equal number of either species alone, suggesting a possible survival benefit from the interaction.