Focus: Microbiome: Human Microbiota and Ophthalmic Disease

The human ocular surface, consisting of the cornea and conjunctiva, is colonized by an expansive, diverse microbial community. Molecular-based methods, such as 16S rRNA sequencing, has allowed for more comprehensive and precise identification of the species composition of the ocular surface microbiota compared to traditional culture-based methods. Evidence suggests that the normal microbiota plays a protective immunological role in preventing the proliferation of pathogenic species and thus, alterations in the homeostatic microbiome may be linked to ophthalmic pathologies. Further investigation of the ocular surface microbiome, as well as the microbiome of other areas of the body such as the oral mucosa and gut, and their role in the pathophysiology of diseases is a significant, emerging field of research, and may someday enable the development of novel probiotic approaches for the treatment and prevention of ophthalmic diseases.     

<Emphasis Type="Italic">Enterococcus faecalis</Emphasis> promotes osteoclast differentiation within an osteoblast/osteoclast co-culture system

Objective

To investigate the effects of heat-killed Enterococcus faecalis ATCC 29212 and P25RC clinical strain (derived from an obturated root canal with apical periodontitis) on osteoclast differentiation within an osteoblast/osteoclast co-culture system.

Results

Heat-killed E. faecalis significantly increased the proportion of multinucleated osteoclastic cells (MNCs) within the co-culture system. The IL-6 level was significantly increased upon exposure to heat-killed E. faecalis. Gene expression levels of NFATc1 and cathepsin K were significantly up-regulated compared to the untreated control. EphrinB2 and EphB4 expressions at both the mRNA and protein levels were also significantly upregulated compared to the untreated control.

Conclusions

Heat-killed E. faecalis can induce osteoclast differentiation within the osteoblast/osteoclast co-culture system in vitro, possibly through ephrinB2-EphB4 bidirectional signaling.

     

A cold-adapted and glucose-stimulated type II α-glucosidase from a deep-sea bacterium <Emphasis Type="Italic">Pseudoalteromonas</Emphasis> sp. K8

Objectives

To express and characterize a putative α-glucosidase, Pagl, from Pseudoalteromonas sp. K8 obtained via genome mining approach.

Results

Pagl was expressed and purified to homogeneity, with a molecular mass of 60 kDa. It was optimally active at pH 8.5 and 30 °C, and showed cold-adapted activity. Pagl exhibited specific activity towards substrates with α-1,4-linkage, with the highest specific activity of 19.4 U/mg for maltose, followed by pNPαG and maltodextrins, suggesting that Pagl belongs to the type II α-glucosidase. Interestingly, the activity of Pagl is significantly enhanced (2.7 times) in the presence of 200 mM glucose.

Conclusion

The unique catalytic properties of Pagl make it an attractive candidate for several industrial applications.

     

Identification and characterization of a novel bifunctional Δ<Superscript>12</Superscript>/Δ<Superscript>15</Superscript>-fatty acid desaturase gene from <Emphasis Type="Italic">Rhodosporidium kratochvilovae</Emphasis>

Objectives

To elucidate the biosynthesis pathway of linoleic acid and α-linolenic acid in Rhodosporidium kratochvilovae YM25235 and investigate the correlation of polyunsaturated fatty acids with its cold adaptation.

Results

A 1341 bp cDNA sequence, designated as RKD12, putatively encoding a Δ¹²-desaturase was isolated from YM25235. Sequence analysis indicated that this sequence comprised a complete ORF encoding 446 amino acids of 50.6 kDa. The encoded amino acid sequence shared higher similarity to known fungal Δ¹²-desaturases that are characteristic of three conserved histidine-rich motifs. RKD12 was further transformed into Saccharomyces cerevisiae INVScl for functional characterization. Fatty acid analysis showed the yeast transformants accumulated two new fatty acids: linoleic acid and α-linolenic acid. Furthermore, mRNA expression level of RKD12 and the content of linoleic acid and α-linolenic acid were increased significantly with the culture temperature downshift from 30 to 15 °C, which might be helpful for the cold adaptation of YM25235.

Conclusion

RKD12 is a novel bifunctional ?¹²/?¹⁵-desaturase gene, and the increased RKD12 mRNA expression level and PUFAs content at low temperature might be helpful for the cold adaptation of YM25235.