Vibrio Natriegens Bacteria - Case Study Example

Introduction

Vibrio natriegens are bacteria which can be found in saline estuarine and marine environments because of its halophilic nature. They mostly live in the estuarine mud intertidal zones. It is a Gram-negative organism and has a doubling time that is among the shortest in any bacterium (Webb 2003)V. natrigens needs about 2% sodium chloride (w/v) for growth. The sodium ions stimulate growth, promote cell membrane stability and aid motility in active transport that depends on Na+ in the Vibrio species (Webb 2003).

This bacterium can increase in number extremely rapidly provided that conditions are optimal. This therefore means that the culture growth rate in the laboratory can be is determined by the environment factors surrounding the process by the environment in the growth media. The growth of bacteria is by binary fission where each cell divides into two. This causes an exponential increase in the number of cells on each level of cell division, thus making the multiplication very rapid.

A bacterium’s growth rate can be determined when the Mean Generation Time (MGT) is estimated. This is the time that a bacterium population takes to double. The MGT indirect estimation method is by sampling the bacterial culture at time intervals that are regular, and then a spectrophotometer is used to measure the absorbance of the culture.

Method

The experiment was performed without change as detailed in O’Hara et al, 2(016).

Results

Broth medium with

0.5% NaCl

Broth medium with

1.0% NaCl

Time

(minutes)

Absorbance at 600nm

Time

(minutes)

Absorbance at 600nm

0

0.175

0

0.196

20

0.201

20

0.257

40

0.286

40

0.381

60

0.403

60

0.496

80

0.528

80

0.579

100

0.623

100

0.611

120

120

Broth medium with

3.5 % NaCl

Broth medium with

7.0 % NaCl

Time

(minutes)

Absorbance at 600nm

Time

(minutes)

Absorbance at 600nm

0

0.225

0

0.202

20

0.283

20

0.244

40

0.481

40

0.252

60

0.627

60

0.357

80

0.800

80

0.457

100

0.912

100

0.653

120

120

Figure 1: Growth of V. natriegens in 0.5% NaCl concentration

Figure 2: Growth of V. natriegens in 1.0% NaCl concentration

Figure 3: Growth of V. natriegens in 3.5% NaCl concentration

Figure 4: Growth of V. natriegens in 7.0% NaCl concentration

Effect of salt on growth rate of V. natriegens

% NaCl supplemented in broth medium

MGT (minutes)

0.5%

40

1.0%

42

3.5%

36

7.0%

30

Figure 5: MGT of V. natriegens grown in media containng 0.5, 1.0%, 3.5% and 7.0% NaCl

The four growth curves each show that the V. natriegens cultures increased in absorbance and therefore number of cells over the course of the experiment.

The mean generation time against percent NaCl concentration shows the effect on salt concentration on the rate of growth of V. natriegens (Figure 5).

From the observed MGTs the concentration of salt affects the growth rate. At 7% concentration, the mean generation time is seen to be highest which shows that this is the optimum concentration for the lowest MGT. This therefore means that at this concentration, multiplication of the bacteria is at its most rapid state. At 7% concentration, the multiplication of V. natriegens is at its optimum, therefore making the MGT to be at its lowest. At the highest MGT, the multiplication rate is low, and this is seen at low concentrations of 1% and 0.5%.

Discussion

These data gives a suggestion of the environment where the bacteria are found. This bacteria is commonly found in marine and estuarine environments where salt concentrations change during the day with the rise and fall of the tide causing the concentration of salt to change as the mud dries out.. This is because the favorable condition for its survival and multiplication is salty conditions.

The observation made on the first graphs showing absorbance against time show an increasing absorbance with increasing time. The bacterial cells multiply which increases the absorbance of the culture medium. Therefore after some time, a high absorbance will be evident because of this.

From the observations made, increased salt concentration causes a reduced mean generation time. The mean generation time being the time that it takes for a population of bacteria to double, it means that the shorter the MGT, the faster the population doubles. Therefore there is a direct relationship between the salt concentration and the growth rate where, a high salt concentration causes a high growth rate.

Vibrio natriegens needs a minimum of 2% (w/v) NaCl for its growth (Webb, 2003). This bacterium benefits a lot from the salt, which makes its growth stimulated. The salt also ensures that the cell membrane is stabilized. The motility and active transport in the cell which depends on sodium ions are also enhanced by increased salty environment (O'Hara et al., 2016).

This bacterium cannot survive well under the conventional conditionsas compared to estuarine and marine environments. V. natriegens requires an approximate of 2% (w/v) NaCl at minimum for its growth. From the data, a decrease in the concentration of sodium chloride caused a decrease in the rate of bacteria multiplication. This therefore shows that since the rate of multiplication is determined by the salt concentration, then lack of salt will mean the bacterial cells will not multiply.