Introduction about the Role of Lux-s gene in Quorum sensing.

Hello all,

Today we are going to see the topic related to quorum sensing and the function of Lux-s genes in regulating cell multiplication and virulence. The world aquaculture industry is facing a lot of struggles in treating diseases. Increased antimicrobial resistance on one side and decreased recovery on another side. In this topic we will discuss the overview about Lux-s genes and its roles in quorum sensing.

We all know that, A. hydrophila is a prevalent and opportunistic pathogen of aquatic organisms, including fish, shrimp, and prawns. Furthermore, A. hydrophila also causes severe diseases in humans, including gastrointestinal illnesses, septicemia, and cellulitis. In several bacterial species, gene expression is controlled by the secretion, detection, and production of extracellular signaling molecules (AI-2) that accumulate in environments in proportion to cell densities of signal molecule-producing cells. This phenomenon is commonly referred to as ‘quorum sensing

Quorum sensing (QS) is a bacterial intercommunication system that controls the expression of multiple genes in response to population density. QS systems use small signal molecules called autoinducers (AIs). When the AIs accumulate to a threshold concentration, the system is activated and directly or indirectly controls the transcription of target genes.

Gram-negative bacteria normally use acylated homoserine lactones (AHLs) as AIs, while gram-positive bacteria use oligopeptide AIs, which act through two-component phosphorelay cascades.

Lux-s associated with the synthesis of AI-2. Lux-s genes are important to mediate the production of AI-2.

Vibrio harveyi can cause infections and diseases in a variety of marine vertebrates and invertebrates, which are harmful to the aquaculture industry. The LuxS quorum-sensing system regulates the expression of virulence factors in a wide variety of pathogenic bacteria.

LuxS/AI-2 is an important quorum sensing system which affects the growth, biofilm formation, virulence, and metabolism of bacteria. LuxS is encoded by the luxS gene, but how this gene is associated with a diverse array of physiological activities in Edwardsiella piscicida (E. piscicida) is not known.Here, an luxS gene mutant strain, the △luxS strain, to identify how LuxS/AI-2 affects pathogenicity. The results showed that LuxS was not found in the luxS gene mutant strain, and this gene deletion decreased E. piscicida growth compared to that of the wild-type strain. Meanwhile, the wild-type strain significantly increased penetration and motility in mucin compared to levels with the △luxS strain.

luxS is found in Gram-positive and Gram-negative bacteria, including A. hydrophila, and performs critical transcription functions in the regulation of genes associated with transport of nucleotides, metabolism, and the synthesis of cell walls or membranes Mutant strains of luxS fail to produce mature biofilms, although increased concentrations of salinity and increased incubation periods also reduce biofilm formation, motility, protease biogenesis, and quorum sensing. Moreover, mutation of the luxS AI-2 synthase gene decreases virulence towards hosts, although virulence can be recovered when AI-2 is added from exogenous sources. From several studies it is clear that Lux-s genes are responsible for inducing virulence in host organisms. On the other hand, several compounds are identified to reduce AI-2 inducers by inhibiting Lux-s gene. Lux-s and AI-2 are correlated in inducing pathogenicity.Studies in inhibiting quorum sensing are limited. 

In the next blog, we will discuss elaborately regarding virulence genes.

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References;

1.https://doi.org/10.1139/cjm-2021-0311

2.10.1128/IAI.74.1.488-496.2006

3.10.1128/IAI.00907-19

4.https://doi.org/10.3390/molecules23102627

Raceway series; Introduction and overview of Raceway aquaculture -1

Hello everyone, 

   Today, we see the importance of Raceway aquaculture system. A successful system for fish (specific to certain species). It is an underrated system and need more research and demonstration for warm water species too. 

'Intensification' is the key criteria need to increase production per unit area in aquaculture. To achieve higher production, the system must be improved in terms of efficiency. 

Top factors need to be considered for designing system, 

1. Carrying capacity

2. Water quality and water availability

3. Species

4. Feed

5. Market availability

In general, Raceway aquaculture system works based on the input of water flow. It is clear that, production is highly depend on the water input and flow. The flowing water effectively removes all the metabolic wastes from the tank and discharge on the other end. 

These systems built by different sizes and dimesions. The most common design is rectangle. The length of the system must not be more than 100 ft. 

Working of the system:

Tanks mostly constructed with cement. It is built on the lower elevation from the ground to get easy access of water. By using gravity, the water is collected and flowed through the tanks. The inlet pipe must be built higher from the tank for better aeration. The water passed into the tanks with high force and collects all the metabolic and feed wastes in the end. At the end, the outlet is constructed to remove this waste and effluents. 

By this, the water quality will be stable and less chance for ammonia. Some cases, supplemental aeration also provided. Though the system is intensified, the feed quality must be good to improve the overall fish health. Because species cultured in the system is highly depends on formulated feed. 

In some cases, people tried to use water by recirculation. In the end of the tank, waste water is collected and used again to the tanks. The success is highly depends on the working and efficiency of the filtration system. 

Fact : Cold water hold more oxygen than warm water. 

To be continued.... 

Thank you for reading.. 

Kindly share and follow my page for more info... 

P. Dhivagar, 

Possible routes for the transmission of disease in shrimp.

Hello everyone! 

Today we are going to see the possible routes for the transmission of disease in shrimp. 

As world population grows, there is increases in protein demand. People finds ways to produce protein food. In that case, Aquaculture serving as a perfect platform for producing protein by the means of culturing aquatic organism. 

On one side, there is a development of broodstock, genetic lines, intensification of culture system, functional feeds and supplements. On the other hand, disease caused by bacteria and virus are threatening the industry. 

Vibrio species are the important pathogens that causes loss to the global aquaculture industry. Whatever we made to control Pathogenicity, it's not upto the mark. In this blog, we are going to look the details about different routes of entry in shrimp. 

In general, we are thinking that, environmental contamination is the main route for transmission of disease from one shrimp to another. But it certainly not. There are different possible routes are suspected for the entry of pathogen into shrimp. 

Possibilities are as follows, 

1. Through feeding of infected shrimp or contaminated feed. 

2. Through the environment. 

3. Transovarially(still remains controversial). 

4. Antennal gland? 

5. From parent? 

The exact portal of entry is still unknown. The gut of the shrimp is completely covered with non-penetrable layer. It act as a barrier against bacteria or virus. But, the antennal gland remains suspected that, it may serve as a port of entry for disease causing pathogens to the shrimp. 

Important function of antennal gland:

1. Hemolymph filtration. 

2. Osmoregulation. 

Susceptibility to disease depends upon the salinity. This paved the way to focus research on antennal gland. It plays major role in osmoregulation. 

Additionally, some of the infection are found in the antennal gland which adds additional support for the suspect of the antennal gland. 

Research conducted by challenging WSSV in shrimp revealed intresting results. Once the WSSV was inoculated into intrabladder of the region. After challenge, urine and hemolymph samples were taken every 12hours.During hyposalinity exposure , shrimp tries to maintains its hemolymph osmolarity by expelling fluid via their excretory organ. Which leads to frequent opening of organ and may lead to pathogen exposure. 

In this case, virus detected after 12hrs of Postinfection in the urine. Only after 24 hrs, the virus detected in the hemolymph of the shrimp. 

This is one of the evidence that suggests the pathogen entry into the shrimp. 

Some relatable questions.. 

1. If we maintain better minerals ratio, will it reduce mortality? 

2. Why minerals and potassium applied most during RMS time in low saline ponds? 

Will continue this topic in next blog. 

There are many questions you can relate with disease and osmoregulation.

Comment your thoughts..... 

Thanks for reading. Share and follow for more. 

Minerals nutrition in shrimp - Important facts.

Hello all!! 

Hope you are doing well. This is Dhivagar and today we are going to see the overview on mineral nutrition in Penaeus vannamei. 

Why it's needed? 

Intensification is changing the scenario and minerals supplementation is must needed one. When you are doing culture in extensive system, there is no need for minerals supplementation, Hence Intensification changing the scenario in aquaculture. 

What is essential? 

Statement from Frieden - An element is considered essential when a deficient intake produces an impairment of function and when restoration of physiological levels of the element prevents or releives the deficiency. 

Minerals requirements of aquatic animals are depends on the environment in which they live. Penaeid shrimp are euryhaline species which can tolerate wide range of salinity. 

Research states, There is no difference in growth and survival when Penaeus vannamei reared in low to higher salinity. 

But, the only matter is composition of minerals in that water. Proportions of individual ions in culture water. It is depends on geographical locations but in general Sodium and Chloride are the major constituents in seawater. Followed by Magnesium and sulphate. 

Minerals requirements of Penaeid species:

Minerals requirements vary with organism. It's absolutely challenging to determine the minerals requirements on different life stages of Penaeus vannamei. Moulting cycle in shrimp plays major role on its minerals requirements. 

During ecdysis, shrimp absorbs most of the minerals from the old exoskeleton by secreting chitinase to breakdown. After shedding it quickly absorbs minerals from water for hardening. 

In this particular time, Haemolymph in shrimp shows higher minerals especially calcium. Hepatopancreas of shrimp shows less compared to haemolymph. Ca, P and K are important minerals that is majorly required during molting and shell hardening. 

In low saline aquaculture, we don't need to make all the minerals in the exact ratio as seawater have. By adding certain minerals can overcome the challenges and requirements. Some minerals plays vital role in oxidation, stress and overall growth performance of shrimp, if the level exceeds, soon it will cause major problem in growth and disease. For instance, we can say supplementation of copper. It is commonly used as a algicide but it's supplementation of less than 0.3 ppm can increase the overall performance of shrimp. There are many other interesting facts about the minerals in growth of shrimp. 

Will continue the same on next blog... 

Comment your thoughts about minerals and it's supplementation in aquaculture. 

Thank you. Follow and share the page for more info. 

Bioremediation in aquaculture.

Dear all, 

Hope you all doing well!!! It's been a long gap.. 

Anyway we will start and share again.. 

Today we will going to discuss about the important process called bioremediation. 

It is the attempt being made to increase the quality of water in aquatic environment. The main role are played by probiotics and enzymes during bioremediation. 

Probiotics is a biological disease Control, particularly using microbiological modulator for disease prevention and received excellent response worldwide. 

Probiotic bacteria competitively exclude the pathogenic bacteria or produce substance that inhibit the growth of pathogenic bacteria in a aquatic environment. 

It also provides essential nutrients and digestive enzymes to increase the overall health of an aquatic animal. 

It also degrade  or decompose the organic matter or other toxic material in the water and improving the quality of water

Probiotics can decompose the fecal and other excreta of fish or prawns and other organic materials which is present in the pond and convert them to carbon dioxide, nitrate, phosphate. 

These inorganic salts provide the nutrition for the growth of micro algae, while the probiotics can grow rapidly and dominating it's population in aquatic environment. 

There are lot of beneficial effects are mediated by microbes. 

1. Neutralization of toxin

2. Suppression of viable count

3. Production of antibacterial compounds

4. Competition for adhesion sites

5. Alterations of microbial metabolism etc.. These probiotics are a better biotechnological tools and everyone must have to use this for their pond applications. 

Enzymes:

These are organic catalyst formed Naturally in living cells. They can accelerate the reactions and they remain unchanged after reaction. 

To regulate the better microflora in aquatic environment and to control pathogenic microorganism, to enhance the decomposition of organic substance, probiotics is a must need one. Use probiotics for your aquatic environment. 

All the best for the successful crop.. 

P. Dhivagar, 

dhivagarfcri2000@gmail.com

Views and perspectives on managing and optimizing cost in shrimp farming.

Hello everyone:

       This is Dhivagar, Today we going to discuss about an important thing that every farmer must need to know. 

Reports:

      Global reports shows reduction in global shrimp production especially from Asian countries. Till now we are facing the price issues. 

     Cost of production exceeds the output cost. 

Here we gonna discuss about some interesting points. 

We have to analyze the various reasons to find solution. 

For the last few days some of the common questions arises on every aquaculturist mind is, why the price is low? 

Is other countries production affects the price in India? 

Here some of the things, we need to consider.. 

1. Farm technology. 

2. Genetic improvement. 

3. Automations ( feeding....) 

4. Expanding international markets. 

5. Advancement in thinking and cooperation. 

Tell the thing, how much you have adopted to your farm from the above points? 

Is extending the days of culture will leads to loss? 

Which is better, going for count or biomass? 

There are many questions there and I am here to answer all of your questions. 

It is important to increase your farm efficiency. One farmer from Tamil Nadu running 2 hp aerator with 4 wheels but other farmer uses 2 hp aerator with 8 wheels. In that place you can see the adaptation.

We can effectively use aqua products, we can optimize the stocking density. 

1. Biosecurity. 

2. Intensification. 

3. Nursery system. 

4. Reduce days of culture. 

5. Adapt new methods. 

6. Increase the efficiency of your farm by adding some values to all inputs. 

7. Automations. 

8. Better farm management practices. 

9. Maintaining primary productivity. 

These are the some of the tips for better farm and results. 

We can reduce the operational inputs effectively for getting good profits. 

We have record on reducing AHCP price for 9-10 rs per kg of shrimp with 45-50 counts. 

Don't fear about white fecal in your ponds. Better management practices will leads to better results. We can reduce the horizontal risk by better biosecurity. Thank you. 

For more information, don't hesitate to contact... 

P. Dhivagar, 

+ 91 9384346193

Is high alkaline water affects growth of shrimp?

Hello everyone:

    It's been a long gap. Hope everyone will find this. Hereafter we will go with frequent posts. I am happy today and wanna share few things regards high alkaline water. 

Issues in Inland region:

      In India, most of the farming areas are found between low to medium saline water. In inland low saline areas, farmers are facing high alkalinity in their bore water(source water). Due to contamination and pollution we can't able to use the water from creek alone. To compensate this, we need to use bore water (to reduce operational costs also). 

Alkalinity and shrimp:

      Alkalinity is an complicated thing which available in different forms in aquatic system. 

      Hopefully, several results shows that, higher alkalinity didn't affect the growth and survival of shrimp. 

     In biofloc system, alkalinity plays a major role. For the formation of floc and decomposition of total ammonia nitrogen, microbes uses dissolved oxygen, inorganic carbon sources. Due to faster decomposition the alkalinity of the system will reduce. 

    Some studies shows heterotropic bacteria uses 5-7 ppm of alkalinity to reduce 1 ppm of TAN. But due to slower growth of autotrophic bacteria, Nitrite in the system will be high. 

Constant water quality:

    In any system, there will be a lot of optimum ranges, but according to alkalinity we can't able to tell the exact range, if you are maintaining the constant parameter then it won't affect shrimp. 

Alkalinity and primary productivity:

     Alkalinity plays important role in primary production of ecosystem. High alkaline water shows high primary production compare to low alkaline waterwater due to excess bicarbonate. 

Alkalinity and heavy metals toxicity:

     High alkaline water prevents metal toxicity in aquatic system. The solubilities of these metals decreases when pH increases. 

Results:

     Results from various studies mentions, the higher survival of shrimp and good growth rate in high alkaline water more than 300 ppm. 

     When the water have high alkalinity, then there will be a chance for low calcium and magnesium ions. 

    High alkaline water also favors for higher biofloc formation, because microbes takes inorganic carbon for their growth. Here I wanna tell, high alkaline water is not an major issue when all other parameters analysed in detail. It may varies on certain parameters. 

Thanks for reading🙃... 

Contact for any query.... 

P. Dhivagar, 

+91 9384346193