Isolation and identification of psychrotrophic lactic acid bacteria in godo, the traditional fermented soy food in Japan

Godo is a traditional fermented soy food made in Aomori prefecture, Japan. It is mainly made of soybeans, rice koji, and salt. Since godo ripens during the long and severe winter in northeast Japan, it is assumed that lactic acid bacteria inhabiting godo have cold tolerance. We aimed to investigate the presence or absence of psychrotrophic lactic acid bacteria in godo. The viable counts of estimated lactic acid bacteria ranged from 10⁶ to 10⁸ cfu/g. In addition, aerobic and anaerobic microorganisms were detected in four godo products though the microbial population differed from sample to sample. Twenty-two bacterial strains were able to be isolated from godo, and all of the isolated strains were Gram-positive and catalase-negative. Some of the isolates grew well at 10°C. The carbohydrate fermentation profile of the selected three strains was determined by API50 CHL analysis. These strains were identified as Leuconostoc mesenteroides, and Latilactobacillus sakei by 16S rRNA gene sequence analysis. Leuconostoc mesenteroides strains HIT231 and HIT252, and Latilactobacillus sakei strain HIT273 could grow at 5°C in MRS broth, but their optimum growth temperature was 20°C-30°C. These results suggest that psychrotrophic lactic acid bacteria presumed to be derived from rice koji are present in godo, which is one of the factors in the low temperature ripening of godo in winter.

Bosea psychrotolerans sp. nov., a psychrotrophic alphaproteobacterium isolated from Lake Michigan water

Three strains of a Gram-stain negative bacterium were isolated from Lake Michigan water. 16S rRNA gene sequence analysis revealed that strain 1131 had sequence similarities to Bosea vaviloviae LMG 28367^T, Bosea lathyri LMG 26379^T, Bosea lupini LMG 26383^T, Bosea eneae CCUG 43111^T, Bosea vestrisii CCUG 43114^T and Boseamassiliensis CCUG 43117^T of 99.8, 99.1, 98.4, 98.4, 98.4 and 98.2 %, respectively. The average nucleotide identity value between strain 1131^T and Bosea vaviloviae Vaf-18^T was 93.4 % and the DNA relatedness was 38 %. The primary cellular fatty acids of strain 1131^T were C16 : 1ω7c and C18 : 1ω7c. The primary polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The major compound in the quinone system was ubiquinone Q-10 and in the polyamine pattern sym-homospermidine was predominant. Additional phenotypic characteristics included growth at 5-35 °C, pH values of pH 5.5-8.0, a salt tolerance range of 0.0-1.2 % (w/v), and production of an unknown water soluble brown pigment. After phenotypic, chemotaxonomic and genomic analyses, this isolate was identified as a novel species for which the name Bosea psychrotolerans is proposed. The type strain is 1131^T (NRRL B-65405=LMG 30034).

Complete Genome Sequence and Comparative Analysis of Synechococcus sp. CS-601 (SynAce01), a Cold-Adapted Cyanobacterium from an Oligotrophic Antarctic Habitat

Marine picocyanobacteria belonging to Synechococcus are major contributors to the global carbon cycle, however the genomic information of its cold-adapted members has been lacking to date. To fill this void the genome of a cold-adapted planktonic cyanobacterium Synechococcus sp. CS-601 (SynAce01) has been sequenced. The genome of the strain contains a single chromosome of approximately 2.75 MBp and GC content of 63.92%. Gene prediction yielded 2984 protein coding sequences and 44 tRNA genes. The genome contained evidence of horizontal gene transfer events during its evolution. CS-601 appears as a transport generalist with some specific adaptation to an oligotrophic marine environment. It has a broad repertoire of transporters of both inorganic and organic nutrients to survive in inhospitable environments. The cold adaptation of the strain exhibited characteristics of a psychrotroph rather than psychrophile. Its salt adaptation strategy is likely to rely on the uptake and synthesis of osmolytes, like glycerol or glycine betaine. Overall, the genome reveals two distinct patterns of adaptation to the inhospitable environment of Antarctica. Adaptation to an oligotrophic marine environment is likely due to an abundance of genes, probably acquired horizontally, that are associated with increased transport of nutrients, osmolytes, and light harvesting. On the other hand, adaptations to low temperatures are likely due to prolonged evolutionary changes.

CsrA impacts survival of Yersinia enterocolitica by affecting a myriad of physiological activities

BACKGROUND

A previous study identified a Yersinia enterocolitica transposon mutant, GY448, that was unable to export the flagellar type three secretion system (T3SS)-dependent phospholipase, YplA. This strain was also deficient for motility and unable to form colonies on Lauria-Bertani agar medium. Preliminary analysis suggested it carried a mutation in csrA. CsrA in Escherichia coli is an RNA-binding protein that is involved in specific post-transcriptional regulation of a myriad of physiological activities. This study investigated how CsrA affects expression of the flagellar regulatory cascade that controls YplA export and motility. It also explored the effect of csrA mutation on Y. enterocolitica in response to conditions that cue physiological changes important for growth in environments found both in nature and the laboratory.

RESULTS

The precise location of the transposon insertion in GMY448 was mapped within csrA. Genetic complementation restored disruptions in motility and the YplA export phenotype (Yex), which confirmed this mutation disrupted CsrA function. Mutation of csrA affected expression of yplA and flagellar genes involved in flagellar T3SS dependent export and motility by altering expression of the master regulators flhDC. Mutation of csrA also resulted in increased sensitivity of Y. enterocolitica to various osmolytes, temperatures and antibiotics.

CONCLUSIONS

The results of this study reveal unique aspects of how CsrA functions in Y. enterocolitica to control its physiology. This provides perspective on how the Csr system is susceptible to adaptation to particular environments and bacterial lifestyles.

A novel ∼34-kDa α-amylase from psychrotroph Exiguobacterium sp. SH3: production, purification, and characterization

An amylase-producing psychrotroph bacterium was isolated from soil and identified as belonging to the genus Exiguobacterium. A novel cold-adapted α-amylase, Amy SH3, was purified from culture medium of this bacterium using acetone precipitation and DEAE-Sepharose anion-exchange chromatography. The molecular mass of the enzyme was estimated about 34 kDa using SDS-PAGE. Biochemical characterization of Amy SH3 revealed that the optimum temperature for maximum activity of Amy SH3 was 37°C. However, Amy SH3 was also active at cold temperatures, showing 13% and 39% activity at 0 and 10°C, respectively. The optimum pH for maximum activity of Amy SH3 was pH 7, whereas the amylase was active over a pH range of 5 to 10. The activity of Amy SH3 was enhanced by Co²⁺ but decreased by Mg²⁺, Mn²⁺, Zn²⁺, Fe²⁺, and Ca²⁺. Amy SH3 was able to retain 76% of its activity in the presence of 0.5% SDS. The K(m) and V(max) of the enzyme were calculated to be 0.06 mg/mL and 4,010 U/mL, respectively. The cold-adapted Amy SH3 seems very promising for applications at ambient temperature.

Screening of microorganisms producing cold-active oxidoreductases to be applied in enantioselective alcohol oxidation. An Antarctic survey

Several microorganisms were isolated from soil/sediment samples of Antarctic Peninsula. The enrichment technique using (RS)-1-(phenyl)ethanol as a carbon source allowed us to isolate 232 psychrophile/psychrotroph microorganisms. We also evaluated the enzyme activity (oxidoreductases) for enantioselective oxidation reactions, by using derivatives of (RS)-1-(phenyl)ethanol as substrates. Among the studied microorganisms, 15 psychrophile/psychrotroph strains contain oxidoreductases that catalyze the (S)-enantiomer oxidation from racemic alcohols to their corresponding ketones. Among the identified microorganisms, Flavobacterium sp. and Arthrobacter sp. showed excellent enzymatic activity. These new bacteria strains were selected for optimization study, in which the (RS)-1-(4-methyl-phenyl)ethanol oxidation was evaluated in several reaction conditions. From these studies, it was observed that Flavobacterium sp. has an excellent enzymatic activity at 10 °C and Arthrobacter sp. at 15 and 25 °C. We have also determined the growth curves of these bacteria, and both strains showed optimum growth at 25 °C, indicating that these bacteria are psychrotroph.