China
Africa
Explore chapters and articles related to this topic
A Review on L-Asparaginase
Published in Se-Kwon Kim, Marine Biochemistry, 2023
The majority of the microbial L-asparaginase is exceptionally intracellular in nature except for a few microbial enzymes that are extracellular, that is, secreted outside the cell (Narayana et al., 2008). Comparatively extracellular enzymes are more preferred to intracellular because of greater collection of enzyme in the culture broth under normal environment, simple extraction and downstream processing. Moreover, the extracellular bacterial L-asparaginase is deficient in protease, and the released protein carried to the medium is generally soluble, biologically active and has a promising N-terminus, free from endotoxins, which ultimately results in a reduction of adverse effects (Amena et al., 2010). Citrobacter sp. has been reported to produce L-asparaginase intracellularly (Bascomb et al., 1975). In the study performed by Hari Krishnan et al. (2016), the isolated marine bacteria obtained from the coastal regions of Kerala showed both intracellular and extracellular L-asparaginase activity. Thus, the screened Bacillus sp. showed extracellular activity while Shewanella sp. showed greater intracellular asparaginase activity.
Antibacterial Activity of Seaweeds and their Extracts
Published in Leonel Pereira, Therapeutic and Nutritional Uses of Algae, 2018
Lavanya and Veerappan (2011) tested the in vitro antibacterial activity of six selected marine algae. Extracts of six seaweed samples, namely Codium decorticatum and Caulerpa scalpelliformis, among others, were selected for antibacterial activity against selected human pathogens, such as species Vibrio parahaemolyticus, Salmonella sp., Shewanella sp., Escherichia coli, Klebsiella pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Proteus mirabilis. All the seaweed extracts have shown moderate antibacterial activity < 10 mm of zone of inhibition, out of which only methanolic extract has shown significant activity. The results of their research showed that the minimum antibacterial activity was found in C. decorticatum.
Characterization of the biofilm grown on 304L stainless steel in urban wastewaters: extracellular polymeric substances (EPS) and bacterial consortia
Published in Biofouling, 2020
Islem Ziadi, Leila El-Bassi, Latifa Bousselmi, Hanene Akrout
In 11 day aged biofilm, Shewanella sp. was isolated from biofilms in the UTUWW and the TUWW. In 11 day aged biofilm in UTUWW: Shewanella putrefaciens (strain IB6; MK779773) and in TUWW: Shewanella xiamenensis (strain IB13, MK778510), Shewanella hafniensis (strain IB14; MK775013), Shewanella oneidensis (strain IB15; MK777979). In the present experimental conditions, phylogenetic analysis showed that Shewanella sp. is the main cluster present in the mature biofilm established on the SS after immersion for 11 days in the UTUWW and the TUWW. Shewanella was reported in previous studies as the bacterium reducing solid Fe3+ oxides to soluble Fe2+ ions in the presence of H2 as an electron donor (Libert et al. 2011; Moreira et al. 2014). El-Naggar et al. (2010) proposed a possible mechanism of electron transfer: the respiration rate of Shewanella is 2.6 × 10−6 electrons/cell/second using lactate as an electron donor. Thus, because of bacterial respiration, and alteration of the hydroxide layers, as a consequence, possible corrosion may occur. Therefore, the presence of Shewanella sp. could locally modify the hydroxide layer, which would initiate the creation of anodic zones and induce a difference in the electrochemical potential conductivity and the development of a localized corrosion process.
Alternative approaches to treat bacterial infections: targeting quorum-sensing
Published in Expert Review of Anti-infective Therapy, 2020
Pipat Piewngam, Janice Chiou, Priyanka Chatterjee, Michael Otto
The AHL-acylase, a member of the Ntn-hydrolase superfamily that was first described in the Variovorax paradoxus strain VAI-C, irreversibly hydrolyzes the amide linkage between the acyl chain and homoserine moiety of AHL molecules. This process releases homoserine lactone and the corresponding fatty acid, which do not exhibit any residual signaling activity. Expression of AiiD, an AHL-acylase from Ralstonia strain XJ12B, in P. aeruginosa led to a reduction in its ability to swarm and produce elastase and toxin [123]. The AHL-acylase AhlM from Streptomyces sp. strain M664 decreases the production of virulence factors in P. aeruginosa, including elastase, total protease, and LasA, by reducing the accumulation of AHLs [124]. AhlM is also a penicillin acylase; and penicillin acylases and AHL acylases can often hydrolyze both β-lactams and AHLs [125]. AHL acylases have been found and characterized in many bacteria, such as Ralstonia erythropolis W2, Comamonas spp. strain D1, Shewanella spp. strain MIB015, and Streptomyces spp [118].