Journal of Microbiology

Review

Bacterial Sialic Acid Catabolism at the Host–Microbe Interface: Jaeeun Kim , Byoung Sik Kim; J. Microbiol. 2023;61(4):369-377. Published online March 27, 2023; DOI: https://doi.org/10.1007/s12275-023-00035-7

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Abstract: Sialic acids consist of nine-carbon keto sugars that are commonly found at the terminal end of mucins. This positional feature of sialic acids contributes to host cell interactions but is also exploited by some pathogenic bacteria in evasion of host immune system. Moreover, many commensals and pathogens use sialic acids as an alternative energy source to survive within the mucus-covered host environments, such as the intestine, vagina, and oral cavity. Among the various biological events mediated by sialic acids, this review will focus on the processes necessary for the catabolic utilization of sialic acid in bacteria. First of all, transportation of sialic acid should be preceded before its catabolism. There are four types of transporters that are used for sialic acid uptake; the major facilitator superfamily (MFS), the tripartite ATP-independent periplasmic C4-dicarboxilate (TRAP) multicomponent transport system, the ATP binding cassette (ABC) transporter, and the sodium solute symporter (SSS). After being moved by these transporters, sialic acid is degraded into an intermediate of glycolysis through the well-conserved catabolic pathway. The genes encoding the catabolic enzymes and transporters are clustered into an operon(s), and their expression is tightly controlled by specific transcriptional regulators. In addition to these mechanisms, we will cover some researches about sialic acid utilization by oral pathogens.

Journal Articles

Relaxed Cleavage Specificity of Hyperactive Variants of Escherichia coli RNase E on RNA I: Dayeong Bae , Hana Hyeon , Eunkyoung Shin , Ji&# , Kangseok Lee; J. Microbiol. 2023;61(2):211-220. Published online February 22, 2023; DOI: https://doi.org/10.1007/s12275-023-00013-z

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Abstract: RNase E is an essential enzyme in Escherichia coli. The cleavage site of this single-stranded specific endoribonuclease is well-characterized in many RNA substrates. Here, we report that the upregulation of RNase E cleavage activity by a mutation that affects either RNA binding (Q36R) or enzyme multimerization (E429G) was accompanied by relaxed cleavage specificity. Both mutations led to enhanced RNase E cleavage in RNA I, an antisense RNA of ColE1-type plasmid replication, at a major site and other cryptic sites. Expression of a truncated RNA I with a major RNase E cleavage site deletion at the 5′-end (RNA I- 5) resulted in an approximately twofold increase in the steady-state levels of RNA I- 5 and the copy number of ColE1-type plasmid in E. coli cells expressing wild-type or variant RNase E compared to those expressing RNA I. These
results
indicate that RNA I- 5 does not efficiently function as an antisense RNA despite having a triphosphate group at the 5′-end, which protects the RNA from ribonuclease attack. Our study suggests that increased cleavage rates of RNase E lead to relaxed cleavage specificity on RNA I and the inability of the cleavage product of RNA I as an antisense regulator in vivo does not stem from its instability by having 5′-monophosphorylated end.

Characterization of a novel phage depolymerase specific to Escherichia coli O157:H7 and biofilm control on abiotic surfaces: Do-Won Park , Jong-Hyun Park; J. Microbiol. 2021;59(11):1002-1009. Published online October 6, 2021; DOI: https://doi.org/10.1007/s12275-021-1413-0

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Abstract: The increasing prevalence of foodborne diseases caused by Escherichia coli O157:H7 as well as its ability to form biofilms poses major threats to public health worldwide. With increasing concerns about the limitations of current disinfectant treatments, phage-derived depolymerases may be used as promising biocontrol agents. Therefore, in this study, the characterization, purification, and application of a novel phage depolymerase, Dpo10, specifically targeting the lipopolysaccharides of E. coli O157, was performed. Dpo10, with a molecular mass of 98 kDa, was predicted to possess pectate lyase activity via genome analysis and considered to act as a receptor- binding protein of the phage. We confirmed that the purified Dpo10 showed O-polysaccharide degrading activity only for the E. coli O157 strains by observing its opaque halo. Dpo10 maintained stable enzymatic activities across a wide range of temperature conditions under 55°C and mild basic pH. Notably, Dpo10 did not inhibit bacterial growth but significantly increased the complement-mediated serum lysis of E. coli O157 by degrading its O-polysaccharides. Moreover, Dpo10 inhibited the biofilm formation against E. coli O157 on abiotic polystyrene by 8-fold and stainless steel by 2.56 log CFU/coupon. This inhibition was visually confirmed via fieldemission scanning electron microscopy. Therefore, the novel depolymerase from E. coli siphophage exhibits specific binding and lytic activities on the lipopolysaccharide of E. coli O157 and may be used as a promising anti-biofilm agent against the E. coli O157:H7 strain.

Changes in the microbial community of Litopenaeus vannamei larvae and rearing water during different growth stages after disinfection treatment of hatchery water: Yafei Duan , Yapeng Tang , Jianhua Huang , Jiasong Zhang , Heizhao Lin , Shigui Jiang , Ruixuan Wang , Guofu Wang; J. Microbiol. 2020;58(9):741-749. Published online July 24, 2020; DOI: https://doi.org/10.1007/s12275-020-0053-0

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Abstract: Microbial communities greatly affect rearing water quality and the larvae health during shrimp hatchery periods. In this study, we investigated the microbial communities of rearing water and larvae of Litopenaeus vannamei after treating hatchery water with different kinds of chemical disinfectants: no disinfectants (Con), chlorine dioxide (ClO2), formaldehyde solution (HCHO), bleach powder (CaClO), and iodine (I2). The water and larval samples were collected from nauplius 6 (N6), zoea 1 (Z1), mysis 1 (M1), and postlarvae 1 (P1) shrimp growth periods. 16S rDNA high-throughput sequencing revealed that the bacterial composition of the rearing water was more complex than that of the larvae, and the bacterial community of the rearing water and the larvae fluctuated significantly at the P1 and Z1 periods, respectively. Disinfectants altered the bacterial diversity and composition of the rearing water and larvae. Specifically, in the rearing water of the P1 period, Proteobacteria abundance was increased in the HCHO group; while Bacteroidetes abundance was decreased in the ClO2, HCHO, and I2 groups but increased in the CaClO group. In the larvae of the Z1 period, Firmicutes (especially Bacillus class) abundance was increased in the CaClO group, but decreased in the ClO2, HCHO, and I2 groups. Network analyses revealed that the genera Donghicola, Roseibacterium, Candidatus-Cquiluna, and Nautella were enriched in the rearing water, while Halomonas, Vibrio, and Flavirhabdus had high abundance in the larvae. The survival of shrimp was influenced by disinfectants that were inconsistent with the bacterial community changes. These results will be helpful for using microbial characteristics to facilitate healthy shrimp nursery.

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