Month: October 2021

A group from University of Moncton, Moncton, NB, Canada, etc. has reported that interactions between Bacillus Spp. and Pseudomonas Spp. promotes plant growth.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8488376/

In this work, Pseudomonas spp. and Bacillus spp. isolates obtained from Canadian soils have been utilized to assess their ability to promote the growth of Cannabis sativa when inoculated alone or in combination treatments in different commercial soil substrates (Promix and Canna coco) commonly used to grow cannabis.

It was demonstrated that single treatments do not stimulate growth promotion under the conditions tested, but combinatorial treatments (Bacillus and Pseudomonas) have a significant positive effect on plant growth.

Here, 223, 825 = Pseudomonas, 979, 1082, 279 = Bacillus. Promix and Canna coco are different types of commercial soil substrates.

Five metabolic pathways could be identified as differently abundant in Canna coco, all of which were also found in Promix:

• oxidative glucose degradation
• creatinine degradation I
• L-lysine biosynthesis II
• S-methyl-5-thio-α-D-ribose 1-phosphate degradation I
• L-methionine salvage cycle III)

These five pathways might be the background of plant growth enhancement, and could easily be linked back to either Pseudomonas spp. or Bacillus spp. metabolism.

Phospholipase metabolic pathway identified in the study is also an important secondary messenger pathway in plants, regulating response to phytohormones and pathogen elicitation. Secreted bacterial phospholipases have the capacity to liberate phosphorus from phospholipids, which the plant could assimilate, potentially augmenting plant growth. The phospholipase pathway together with sugar metabolism in Pseudomonas spp. might significantly increase the availability of essential soil nutrients for the plant and promote plant growth.

A group from Georg-August-University Göttingen, Wilhelmsplatz 1, 37073 Göttingen, Germany, etc. has reported that syncytium formation (cell-to-cell fusion) could contribute to efficient spread of the SARS-CoV-2 delta variant.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8487035/

Vero, 293T, Caco-2, and Calu-3, these cell lines express endogenous ACE2 and Vero, Caco-2, and Calu-3 cells are often used for infection studies with authentic SARS-CoV-2. The delta variant S protein mediated entry into 293T and Vero cells with the same efficiency as the wild-type (WT) S protein, while entry into Caco-2 and Calu-3 cells was enhanced by 1.5 times and 2.0 times comparing with wild type. However, any increased ACE2 binding of the delta variant S protein was not observed, suggesting that increased entry into Caco-2 and Calu-3 cells was not due to augmented ACE2 binding.

SARS-CoV-2 S protein-driven syncytium formation is believed to contribute to the increased infectivity of the delta variant. To confirm syncytium formation drove by the delta variant, human lung cell line A549 expressing high level of ACE2 was adopted. As expected, WT S led to the formation of syncytia, while syncytia formation was not observed when cells were transfected with empty expression plasmid. Strikingly, the delta variant S protein caused more and larger syncytia, and quantification of cell-to-cell fusion revealed that fusion by the delta variant S protein was ∼2.5-fold more effective as compared to the WT S protein.

In conclusion, syncytium formation (cell-to-cell fusion) could contribute to efficient spread of the delta variant.

A group from Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA, etc. has reported that SARS-CoV-2 viral replication in human macrophages enhances an inflammatory cascade.
https://www.biorxiv.org/content/10.1101/2021.09.27.461948v1

In order to identify SARS-CoV-2 infected cells, authors used MISTRG6-hACE2 mice (humanized-ACE2 mice). As expected, SARS-CoV-2 viral RNA was detected in epithelial cells, the main targets of SARS-CoV-2 infections. Surprisingly, however, human immune cells also had similar levels of viral RNA. To better visualize and characterize these cells, MISTRG6-hACE2 mice were infected with a reporter strain of virus, SARS-CoV-2-mNG19. The majority of epithelial cells (EPCAM+) in bronchioalveolar lavage (BAL) but only a small proportion of total lung epithelial cells were infected with SARS-CoV-2 as measured by mNG expressing cells. Human immune cells showed a clear mNG signal, and mNG+ human immune cells were predominantly human macrophages.

Since macrophages are phagocytic, it is needed to address whether the SARS-CoV-2 viral RNA in these cells replicates in these cells or is simply acquired by phagocytosis of infected cells or debris. To achieve this, we first characterized the mNG signal in human macrophages from MISTRG6 mice that were not transduced with hACE2. In these mice, epithelial cells were not infected with SARS-CoV-2. These mice had however similar levels of mNG signal in the human macrophages of AAV-ACE2 mice, arguing that viral uptake by human macrophages is independent of infected epithelial cells. To determine whether SARS-CoV-2 replicates in human macrophages, the key characteristics of viral replication, viral replication products, subgenomic RNA, double stranded RNA (dsRNA), and the key replicative enzyme RNA dependent RNA polymerase (RdRp) were evaluated.
(1) Quantified genomic and subgenomic viral RNA in mNG+ vs mNG- epithelial or human immune cells at 4dpi or 14dpi. Only mNG+ epithelial cells and mNG+ human immune cells showed detectable subgenomic viral RNA. The levels of subgenomic RNA in human immune cells and epithelial cells were similar, suggesting a similar extent of viral replication in human immune cells and epithelial cells.
(2) Stained for dsRNA in mNG+ cells to determine whether the mNG signal colocalized with dsRNA (an exclusive product of viral replication). As expected, mNG and dsRNA were detectable and colocalized in both epithelial cells and in macrophages.
(3) Visualized viral RdRp in human macrophages.

In addition, the existence of antibody mediated viral uptake by macrophages was confirmed by treating infected mice with monoclonal antibodies against Spike protein of SARS-CoV-2, starting at 35 hours post infection (hpi). It was clearly shown that monoclonal antibody treatment increased the percentage of mNG+ macrophages in lungs.

A group from Far Eastern Branch of Russian Academy of Sciences, Vladivostok, Russia has reported on a new lectin, GYL, extracted from bivalve Glycymeris yessoensis.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8466245/

A lectin named GYL is a dimeric protein with a molecular mass of 36 kDa, as established by SDS-PAGE and MALDI-TOF analysis, consisting of 18 kDa subunits linked by a disulfide bridge.

The peptide sequence of GYL showed no significant homology with other lectins listed in the BLAST, however, the National Center for Biotechnology Information (NCBI) Conserved Domain Search program identified conserved EPN (Glu-Pro-Asn) and WND (Trp- Asn- Asp) motifs in the GYL peptide sequence, which are characteristic of the CRD of C-type lectins (CTL).

GYL was widely expressed throughout the tissues of healthy clams, however, levels of the lectin in the hemolymph and mantle were found to be 3.5- and 2.4-fold greater, respectively, than that found in the gonads.

GYL agglutinated all erythrocytes tested, suggesting that this activity is not highly specific. Although the detailed glycan binding specificity is not clearly shown, it was found that GYL preferentially bound peptidoglycan (PGN) and LPS expressed on bacteria cell walls, but had little binding activity toward β-1,3-glucan and mannan, which are usual components of the yeast cell wall.

Taking these things into consideration, it was suggested that GYL plays an important role in the immune defense of the clam against pathogenic microorganism infections. Temporal expression levels of GYL in the hemolymph following V. proteolyticus stimulation and diesel fuel exposure were investigated. Amazingly, the expression levels of lectin increased about 25-fold at 48 h post-injection, suggesting that bacterial infection and anthropogenic factors had a significant effect on the clam, causing them to increase the synthesis of GYL as a protective molecule.

A group from The Institute of Medical Science, The University of Tokyo, etc. has reported that Antibody-Dependent Enhancement of SARS-CVoV-2 infection to immune cells is real.
https://journals.asm.org/doi/10.1128/mBio.01987-21

Viruses infect cells mainly via specific receptors at the cell surface. Antibody-dependent enhancement (ADE) of infection is an alternative mechanism of infection for viruses to infect immune cells that is mediated by antibodies and IgG receptors (FcγRs).

Authors generated BHK cells stably expressing human FcγRs (FcγRIA, FcγRIIA, or FcγRIIIA) or human angiotensin-converting enzyme 2 (hACE2) (the entry receptor for SARS-CoV-2). Wild-type BHK cells lack human ACE2 expression and are not susceptible to SARS-CoV-2.

BHK cells were infected with a firefly luciferase-expressing vesicular stomatitis virus (VSV) lacking the VSV-G gene and pseudotyped with SARS-CoV-2 spike (VSV-SARS2-S). Although BHK-hACE2 cells were susceptible to VSV-SARS2-S, the BHK-FcγRIA, BHK-FcγRIIA, and BHK-FcγRIIIA cells were not susceptible due to the lack of hACE2. However, using convalescent-phase plasma from COVID-19 patients and incubated with VSV-SARS2-S, it was found that two types of FcγRs, FcγRIIA and FcγRIIIA, mediate ADE of SARS-CoV-2 infection in the presence of ACE2.

It was also confirmed that SARS-CoV-2 infection is enhanced by convalescent-phase plasma in primary macrophages.