Engelbrecht, L. | bioRxiv Science

bioRxiv2023

Altered neutrophil extracellular traps in response to Mycobacterium tuberculosis in persons living with HIV with no previous TB and negative TST and IGRA

Persons living with HIV (PLWH) have an increased risk for tuberculosis (TB). After prolonged and repeated exposure, some PLWH never develop TB and test persistently negative in tests of immune sensitization tuberculin skin test (TST) and interferon gamma release assays (IGRA) for Mycobacterium tuberculosis (Mtb). This group has been identified and defined as HIV+ persistently TB, tuberculin and IGRA negative (HITTIN). To investigate potential innate mechanisms unique to individuals with the HITTIN phenotype we compared their neutrophil Mtb infection response to that of PLWH, with no TB history, but who test persistently IGRA positive, and tuberculin positive (HIT). Neutrophil samples from 17 HITTIN (PMNHITTIN) and 11 HIT (PMNHIT) were isolated and infected with Mtb H37Rv for 1h and 6h. RNA was extracted and used for RNAseq analysis. At 1h of Mtb infection, PMNHITTIN displayed 151 significantly upregulated and 40 significantly downregulated differentially expressed genes (DEGs) and PMNHIT 98 significantly upregulated and 11 significantly downregulated DEGs. At the 6h timepoint, PMNHITTIN displayed 3106 significantly upregulated and 3548 significantly downregulated DEGs while PMNHIT had 3816 significantly up- and 3794 significantly downregulated DEGs. There was no significant differential transcriptional response at 1h between infected PMNHITTIN and PMNHIT. However, when contrasting the log2FC 6h infection response to Mtb from PMNHITTIN against PMNHIT, 2285 genes showed significant differential response between the two groups. Apoptosis and NETosis were key pathways linked to the enrichment of genes in PMNHITTIN when contrasted to PMNHIT after 6h infection with Mtb. Fluorescence microscopy revealed relatively lower neutrophil extracellular trap formation and cell loss in PMNHITTIN compared to PMNHIT, showing that PMNHITTIN have a distinct response to Mtb.

genetics↗

bioRxiv2020

Disruption of glycogen metabolism alters cell size in Escherichia coli

The availability of nutrients impacts cell size and growth rate in many organisms. Research in E. coli has traditionally focused on the influence of exogenous nutrient sources on cell size through their effect on growth and cell cycle progression. Utilising a set of mutants where three genes involved in glycogen degradation - glycogen phosphorylase (glgP), glycogen debranching enzyme (glgX) and maltodextrin phosphorylase (malP) - were disrupted, we examined if endogenous polyglucan degradation affects cell size. It was found that mutations to malP increased cell lengths and resulted in substantial heterogeneity of cell size. This was most apparent during exponential growth and the phenotype was unaccompanied by alterations in Z-ring occurrence, cellular FtsZ levels and generation times. {Delta}malP mutant cells did, however, accumulate increased DnaA amounts at late growth stages indicating a potential effect on DNA replication. Replication run-out experiments demonstrated that this was indeed the case, and that DNA replication was also affected in the other mutants. Bacteria with a disruption in glgX accumulated glycogen and protein inclusion bodies that coincided with each other at inter-nucleoid and polar regions.

microbiology↗