Bacteria decline phase

The same effect of bacterial contaminations was observed with an electronic nose equipped with CP sensors in an antibiotic fermentation with Micro-monospora carbonacea [34]. Infections of E. coli and Gram-positive bacteria can be discriminated in the plot. The same culture also exhibited characteristic response patterns at the different fermentation stages over a nine-day period. The character of the trajectory in the PCA mirrored the growth phase, the antibiotic synthesis phase as well as the declination phase. The starting point of the trajectory almost coincided with the end point. 

The growth phase lasts for several days and raises the population to around 10 UFC/ml or more. Evidently, its duration also depends on the composition of the medium. The subsequent stationary phase also varies. The bacteria then begin the decline phase. As soon as the mahc acid is completely transformed, sulfiting is used to eliminate the bacteria as quickly as possible. 

Both methods give the same results for bacterial suspensions in the growth phase. When they move into the stationary, and then the decline phase, the difference between the results increases. While counting by epifluorescence shows a slight decrease in the number of cells, there is a sharp drop in the number of colonies visible. This difference may be explained by the fact that part of the population of fluorescent cells is still biologically active but is incapable of the metabolic and physiological functions necessary for multiplication. They are described as viable, non-cultivable (VNC) cells. Table 6.3 shows the lactic bacteria count after sulfiting a wine. 

In phase D, the phase of decline, bacteria are actually dying due to the combined pressures of food exhaustion and toxic waste accumulahon. 

Starter bacteria. The starter culture reaches maximum numbers at the end of the manufacturing phase. Their numbers then decline at a rate depending on the strain, typically by 2 log cycles within 1 month. At least some of the non-viable cells lyse at a rate dependent on the strain. As far as is known, the only extracellular enzyme in Lactococcus, Lactobacillus... 

The curve is ordinarily divided into different phases. Lag phase corresponds to no growth or even a decline in number. After the lag period, the growth rate continuously increases and the bacteria are in the exponential or logarithmic phase in which the multiplication rate is most rapid and can be represented by a straight line on a log-linear plot. Then, the bacteria reach the maximum cell number and the multiplication rate decreases. The number of bacteria remains constant and this phase is called the stationary phase. The death phase occurs when the cell number decreases at a faster rate than the rate new cells are formed. 

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