Corynebacterium glutamicum possesses β-N-acetylglucosaminidase

Matano C, Kolkenbrock S, Hamer SN, Sgobba E, Moerschbacher BM, Wendisch VF. Corynebacterium glutamicum possesses β-N-acetylglucosaminidase. BMC Microbiology. 2016;16(1): 177.Background In Gram-positive Corynebacterium glutamicum and other members of the suborder Corynebacterianeae, which includes mycobacteria, cell elongation and peptidoglycan biosynthesis is mainly due to polar growth. C. glutamicum lacks an uptake system for the peptidoglycan constituent N-acetylglucosamine (GlcNAc), but is able to catabolize GlcNAc-6-phosphate. Due to its importance in white biotechnology and in order to ensure more sustainable processes based on non-food renewables and to reduce feedstock costs, C. glutamicum strains have previously been engineered to produce amino acids from GlcNAc. GlcNAc also is a constituent of chitin, but it is unknown if C. glutamicum possesses chitinolytic enzymes. Results Chitin was shown here not to be growth substrate for C. glutamicum. However, its genome encodes a putative N-acetylglucosaminidase. The nagA 2 gene product was active as β-N-acetylglucosaminidase with 0.27 mM 4-nitrophenyl N,N’-diacetyl-β-D-chitobioside as substrate supporting half-maximal activity. NagA2 was secreted into the culture medium when overproduced with TAT and Sec dependent signal peptides, while it remained cytoplasmic when overproduced without signal peptide. Heterologous expression of exochitinase gene chiB from Serratia marcescens resulted in chitinolytic activity and ChiB secretion was enhanced when a signal peptide from C. glutamicum was used. Colloidal chitin did not support growth of a strain secreting exochitinase ChiB and β-N-acetylglucosaminidase NagA2. Conclusions C. glutamicum possesses β-N-acetylglucosaminidase. In the wild type, β-N-acetylglucosaminidase activity was too low to be detected. However, overproduction of the enzyme fused to TAT or Sec signal peptides led to secretion of active β-N-acetylglucosaminidase. The finding that concomitant secretion of endogenous NagA2 and exochitinase ChiB from S. marcescens did not entail growth with colloidal chitin as sole or combined carbon source, may indicate the requirement for higher or additional enzyme activities such as processive chitinase or endochitinase activities

Alternative carbon sources for Corynebacterium glutamicum: chitin and its derivates

Matano C. Alternative carbon sources for Corynebacterium glutamicum: chitin and its derivates. Bielefeld; 2014

Anodic dissolution model with diffusion-migration transport for simulating localized corrosion

International audienceA one-dimensional model for simulating localized corrosion is developed, incorporating time-dependent diffusion-migration transport. The model is applied to iron with the Butler-Volmer formula as the dissolution law, and both crevice and pit configurations are simulated. A finite-difference ALE scheme is used for the numerical computation of the solutions of this free boundary problem. The results show that the dissolution rate increases with chloride concentration and metal potential, and migration plays, most of the time, a significant role in species transport for both crevice and pit configurations. The evolution of the repassivation potential with pit depth is computed and is in good agreement with experimental results. The time-dependent model under consideration provides more accurate quantitative results for concentration profile and crevice depth than stationary models

Anodic dissolution model with diffusion-migration transport for simulating localized corrosion

International audienceA one-dimensional model for simulating localized corrosion is developed, incorporating time-dependent diffusion-migration transport. The model is applied to iron with the Butler-Volmer formula as the dissolution law, and both crevice and pit configurations are simulated. A finite-difference ALE scheme is used for the numerical computation of the solutions of this free boundary problem. The results show that the dissolution rate increases with chloride concentration and metal potential, and migration plays, most of the time, a significant role in species transport for both crevice and pit configurations. The evolution of the repassivation potential with pit depth is computed and is in good agreement with experimental results. The time-dependent model under consideration provides more accurate quantitative results for concentration profile and crevice depth than stationary models

Transcription of sialic acid catabolism genes in Corynebacterium glutamicum is subject to catabolite repression and control by the transcriptional repressor NanR

Uhde A, Brühl N, Goldbeck O, et al. Transcription of sialic acid catabolism genes in Corynebacterium glutamicum is subject to catabolite repression and control by the transcriptional repressor NanR. J Bacteriol. 2016;198(16):2204-2218

Additional file 1: of Corynebacterium glutamicum possesses β-N-acetylglucosaminidase

Table S1. Oligonucleotides used in this study. Figure S1 Plasmid maps of pVWEx1-nagE [A] and pEKEx3-SP0955-chiB-SP0955-nagA2 [B]. Functional elements of the plasmid pVWEx1-nagE include antibiotic markers (Km, kanamycin), origin of replication (pHM1519), nagE (GlcNAc-specific PTS from Corynebacterium glycinophilum DSM45794). Functional elements of the plasmid pEKEx3-SP0955-chiB-SP0955-nagA2 include relevant restriction sites, antibiotic markers (Spec, spectomycin), origin of replication (pBL1), tat (SP0955), chiB (chitinase B, Serratia marcescens), nagA2 (β-N-acetylglucosaminidase, C. glutamicum). (DOCX 246 kb

Blockade of T cell costimulation reveals interrelated actions of CD4(+) and CD8(+) T cells in control of SIV replication

In vivo blockade of CD28 and CD40 T cell costimulation pathways during acute simian immunodeficiency virus (SIV) infection of rhesus macaques was performed to assess the relative contributions of CD4(+) T cells, CD8(+) T cells, and Ab responses in modulating SIV replication and disease progression. Transient administration of CTLA4-Ig and anti–CD40L mAb to SIV-infected rhesus macaques resulted in dramatic inhibition of the generation of both SIV-specific cellular and humoral immune responses. Acute levels of proliferating CD8(+) T cells were associated with early control of SIV viremia but did not predict ensuing set point viremia or survival. The level of in vivo CD4(+) T cell proliferation during acute SIV infection correlated with concomitant peak levels of SIV plasma viremia, whereas measures of in vivo CD4(+) T cell proliferation that extended into chronic infection correlated with lower SIV viral load and increased survival. These results suggest that proliferating CD4(+) T cells function both as sources of virus production and as antiviral effectors and that increased levels of CD4(+) T cell proliferation during SIV infections reflect antigen-driven antiviral responses rather than a compensatory homeostatic response. These results highlight the interrelated actions of CD4(+) and CD8(+) T cell responses in vivo that modulate SIV replication and pathogenesis