Kushneria konosiri

Introduction

Microbes have been an extremely important part of human history for thousands of years. They assist us in numerous daily functions and allow for life on Earth to run smoothly. One of their most important functions is in the production of food products, especially in those that are fermented. Fermented food products have been a staple in human diets due to their unique tastes, decreased perishability, and possible health benefits. An example of a popular fermented food product is daemi-jeot. This is a salt- fermented dish prepared commonly in Korea from Konosirus punctatus, a species of fish known as the dotted gizzard shad. This fish falls within the same family as sardines and anchovies (1). To make this traditional Korean dish, the fish is heavily salted and left to ferment. Like many other food products that undergo fermentation, daemi-jeot is able to be made due to the microbial interactions within its environment. However, bacterial populations found within this product are still being understood and discovered. Kushneria konosiri is the proposed name of a novel bacterial strain, strain X49T, discovered within this Korean fermented fish product (3). Kushneria konosiri is a halophilic, Gram-negative, and oval or rod-shaped organism. It is motile and contains a single flagellum that branches out from the cell. Metabolically, it is obligately aerobic. The optimum growth conditions for this bacterial strain are at 15–25 degrees Celsius, pH 5.0–7.0 and in the presence of 11–19 % (w/v) NaCl (3). Within its environment, its halophilic properties characteristic of members within its family (4) allow this microbe to survive and outcompete other microorganisms by withstanding the high salt concentrations surrounding it during the preparation of daemi-jeot. This is due to its development of several functional genes and its ability to perform carotenoid biosynthesis (2). With these adaptations this particular strain can survive in environments with salt concentrations up to 26% w/v NaCl (3). This bacterium thrives within this environment and could be a contributor to the fermentation process of daemi-jeot as it produces acids through a majority of its metabolic processes (3).

Classification

Higher Order Taxa

Eubacteria (Kingdom); Bacteria (Domain); Proteobacteria (Phylum); Gammaproteobacteria (Class); Oceanospirillales (Order); Halomonadaceae (Family); Kushneria (Genus)

Species

Kushneria konosiri, type strain X49T (Accession GU198748)

NCBI: Taxonomy

JGI:GOLD

Phylogenetic Relatedness

Kushneria konosiri is a Halomonadaceae that belongs to the genus Kushneria. This genus was discovered previously as a reclassification of a cluster of species from the genus Halomonas (5). To discover Kushneria konosiri, researchers isolated genomic DNA using previous methodology (6) and used 16S and 23S rRNA gene sequencing methods in order to determine the genetic relatedness of this bacterial strain. A phylogenetic tree containing this organism was constructed using the neighbor joining method. It was used by researchers to compare 16S rRNA sequences of this species with others in the Kushneria genus. In the same study, a separate tree was constructed using 23S rRNA sequences but it revealed similar information to the results of 16S rRNA (2). This bacterium is most closely related to the species Kushneria marislavi a halophilic bacteria discovered from a water sample in the Yellow Sea (7). Through average-nucleotide identity tests, their relatedness level was found to be just below 90% (3). This indicated that this strain was in fact a novel species within the Kushneria genus.

Ecological Habitat

This bacterium was isolated from the liquid portion of the Korean fermented seafood product daemi-jeot. This food product is a variation of the popular Korean dish jeotgal. Jeotgal is a popular Korean dish consumed either as a condiment or as a seasoning to other dishes. In general, all forms of jeotgal are made by heavily salting a particular type of seafood such as fish, shellfish, and squid and can be characterized by their main ingredients (8). Daemi-jeot in particular comes from the adductor muscle, stomach, and intestines of the dotted gizzard shad (9). The liquid environment of Kushneria konosiri was isolated from was not tested extensively for abiotic physical and chemical factors as it came from a homemade food product bought at a market on the coast of South Korea (3). However, as this type of dish is relatively common in Korean cuisine and is prepared in a traditional manner (8), some assumptions can be made about these factors. Since daemi-jeot is fermented using solar salt rather than traditional purified salt we can assume that within this environment there are a significant amount of micronutrients and minerals such as K, Mg, and Ca (10). The NaCl concentration is also likely significantly high within this environment with as some forms of jeotgal are prepared in environments around 25% w/v NaCl (8, 11). During the fermentation process occurring within a common jeotgal environment there is an overall decrease in pH consisting of a drop in pH initially followed by a small increase after some time (12). Oxygen concentration and temperature are also unknown for this particular environment but as this product commonly is left to sit out at the market (Fig. 2) we can assume that it was exposed to atmospheric levels of oxygen and varying temperatures that were likely mild at the time as this sample was collected in April (2).

Environments of other species within the Kushneria Genus

The genus Kushneria is relatively novel and small, containing only 9 classified species (13). In general, Kushneria species are located in hypersaline environments. Species have been located in areas such as leaves of the black mangrove in Puerto Rico (14), the Yellow Sea in Korea (7), salt mines in Pakistan (15), and even within traditional Chinese cured meat (6). All members of this genus are also aerobic so they must be in the presence of oxygen to grow (13). Within their environment, they are not known to form spores (5).

Significance to the Environment

Since this bacterium is obligately aerobic and heterotrophic, it cycles nutrients through aerobic cellular respiration, obtaining its source of carbon for respiration by consuming organic materials in its environment (16). The organic materials are most likely the sugars and fats present in within the fish. While it goes through aerobic cellular respiration, being within a high-sodium environment, Kushneria konosiri is not able to form a typical proton gradient and must establish transmembrane gradients with other cations, likely sodium in its environment, and pumps them in using a modified version of ATP synthase to phosphorylate ADP (16). As this species is catalase-positive (3), through its process of aerobic cellular respiration this bacterium uses catalase to convert toxic hydrogen peroxide produced through its electron transport chain into water and oxygen gas (16). While there is an understanding of the general metabolic processes this bacterium can perform, not much is known about the exact significance that Kushneria konosiri has on the environment of daemi-jeot. While it may have some influence on the process of fermentation through the production of acid in its metabolic processes, Kushneria konosiri is not known to perform any fermentation and is also not able to reduce nitrate (3). With that being said, however, some significance of this bacterium results in its ability to outcompete other microorganisms for nutrients and space within this hypersaline environment. There is not much known about how human induced changes to its environment impact the development, evolution, and spread of Kushneria konosiri. However, increased global production of plastic products has had a negative impact in marine environments and thus could indirectly harm this bacterium. Recently, Konosirus punctatus have been shown to have high levels of microplastic pollution within their gut as a result of increased plastic pollution within their ecosystem (17). While the effects of increased microplastic contamination on food product microbial environments has not been studied extensively, previous studies have indicated adverse effects on normal physiological processes within marine microorganisms due to microplastic exposure (18). In the future, microplastics could have similar harmful effects on organisms present within seafood-based products as it has been proposed that microplastics can have bioaccumulation effects within the food chain (19).

Ecological Lifestyle and Interactions

Kushneria konosiri is a free-living bacterium within its environment (2). It is also an obligate aerobe and a heterotroph. While the specific lifestyle and interactions of this bacterium were not studied extensively, Kushneria konosiri likely interacts with a very wide variety of microorganisms as traditionally there is not much purification done with the fish products in jeotgal. Along with this, as with most multicellular organisms, a wide variety of pathogens and other microorganisms are found to coexist within the gut and surrounding tissues of the dotted gizzard shad. However, after the addition of solar salt to the fish many of those microorganisms likely died due to increased osmotic pressure. For the most part, we can assume that Kushneria konosiri interacts with halotolerant/halophilic microorganisms. The particular microbial population for the specific environment that Kushneria konosiri was isolated from, daemi-jeot, has not been studied extensively. However, many other types of jeotgal have been studied and allow us to make assumptions about that environment. Generally, through the process of fermentation in jeotgal products succession evens occur within the environment (8). This is likely due to the changes in salinity and pH during fermentation. Bacteria are not believed to be major contributors to proteolysis within jeotgal, but many are known to be the driving forces for the ripening, distinct flavoring, and for the decrease in pathogenic microbes within the environment (8, 20). The most common microorganisms present in jeotgal products are Bacillus, Brevibacterium, Flavobacterium, Micrococcus, Pediococcus, Pseudomonas, and Staphylococcus (8).

Along with those bacteria, Halobacterium, and Halomonas are also common as they are resistant to high levels of salt (8). Lactobacillus species have been shown to have antimicrobial activity to pathogens (8). In a study monitoring a jeotgal product containing anchovy, a close relative to Konosirus punctas, during its fermentation process it was shown that as fermentation goes along there is a general decrease in the population of microbes within the sample. Along with that researchers found that during the middle stage of fermentation, Pediococcus and yeasts dominated and were assumed to be the main fermenters of the fish product (21). It has also been shown that a succession from Proteobacteria to Firmicutes is a common occurrence within jeotgal products (8). However, with that being said, there is an extremely wide diversity of microbes present within each distinct jeotgal product. The main seafood base and spices added to each are unique and likely are the main reason for that large diversity. While we can assume that some microbes are present and have general functions, it is also known that there are a large number of microbes that have not been identified yet that are present in jeotgal products (8). Thus, the exact microbial interactions and populations present in daemi-jeot require more extensive research in order to be fully understood.

Although the influence of this bacterium on the jeotgal environment is relatively unknown, Kushneria bacteria have been shown to have influence on the fermentation of other food products. Bacteria of this genus were shown to be a core microbe of a Chinese food product called Panxian ham (22). In a research study on Panxian ham, bacteria of the Kushneria genus were found to be associated with the production of organic acids such as succinic and malic acids. Succinic acid is important in producing sour and umami tastes in that ham product (22). Similar to jeotgal, Panxian ham was shown to have multiple succession events that occur during its fermentation process. Proteobacteria dominated the raw and post salting stages and ultimately Firmicutes ended up dominating the resting and ripening stages of this product. The population of Kushneria bacteria was found to be largely increased during the final stages of ripening for this product due to increased salt content (22). Due to the similarities in the stages of fermentation for these products, we can assume the Kushneria konosiri also grew in abundance during this period for daemi-jeot,

Significance to Humans

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Describe how this microbe has influenced human society now or in the past.
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Cell Structure

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Colony morphology (size, shape, texture, pigmentation, smell?, etc…)
Cell morphology
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Motility
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Cell Metabolism

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Provide a physical and metabolic description of the organism. Are there special diagnostic media or methods to distinguish this microbe from close relatives?

Optimal abiotic growth conditions (temperature, salinity, oxygen, UV)
Carbon growth sources
Other metabolic abilities
Any other unique abilities (e.g toxin production, antibiotic resistance, etc...)

.

Genome Structure, Content, and/or Gene Expression

LO: Genome structure and content provide insight into a microbe's evolutionary history, ecological niche, and interactions with hosts and other microbes.

LO: Mutations and horizontal gene transfer, with an immense variety of microenvironments, have selected for a huge diversity of microorganisms.

LO: The regulation of gene expression is influenced by external and internal molecular cues and/or signals.

LO: Cell genomes can be manipulated to alter cell function.

LO: Genetic variations can impact microbial functions (e.g. in biofilm formation, pathogenicity, and drug resistance).

Metrics

Genome size
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number of chromosomes and/or plasmids?
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Relevance

Why was this organism sequenced?
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Interesting Feature

LO: Mutations and horizontal gene transfer, with an immense variety of microenvironments, have selected for a huge diversity of microorganisms.

LO: Human impact on the environment influences the evolution of microorganisms (e.g., emerging diseases and the selection of antibiotic resistance).

LO: Because the true diversity of microbial life is largely unknown, its effects and potential benefits have not been fully explored.

Describe in detail one particularly interesting aspect of your organism.

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In ~3 sentences propose WHY more research and WHAT kind of new research should be done on this organism and others like it. Connect this to the learning objective about the importance of microbial diversity
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References

Each section must have at least 2 references to the primary peer-reviewed literature and at least 1 reference to a reference book like Bergey’s Manual or resources available on the NCBI bookshelf. Also, link out to reputable blogs like Small Things Considered (https://schaechter.asmblog.org/schaechter/), MostlyMicrobes (http://www.mostlymicrobes.com/), Sarah’s Little World (https://sarahs-world.blog/), professional websites American Society for Microbiology (https://asm.org/browse-asm), Microbiology Society (https://microbiologysociety.org/), and podcasts like the many by ASM (https://asm.org/podcasts), This Podcast Will Kill You (https://thispodcastwillkillyou.com/), etc… These should also be cited in the reference section.

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Journal

Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500. https://doi.org/10.1099/00207713-50-2-489

Book

Surname Initials. Book title. Edition - if available: Publisher, place of publication; Year .

Books with Editors

Beers MH, Porter RS, Jones TV, Kaplan JL, Berkwits M, editors. The Merck manual of diagnosis and therapy. 18th ed. Whitehouse Station (NJ): Merck Research Laboratories; 2006.

Authored chapter in edited publication;;

Glennon RA, Dukat M. Serotonin receptors and drugs affecting serotonergic neurotransmission. In: Williams DA, Lemke TL, editors. Foye's principles of medicinal chemistry. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2002.

Electronic

World Health Organization (WHO). Mortality country fact sheet 2006 [internet]. Geneva: WHO; 2006. Available from: www.who.int/whosis/mort_emro_pak_pakistan.pdf

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