Microbiology - Bacteria Growth, Reproduction, Classification

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binary fusion so bacteria reproduced by binary fusion so here we have a simple bacteria with the DNA inside circular DNA might I say nuclear matter next the DNA will be replicated during binary fusion replicated like so and then the DNA will divide and what's called a transverse septum will be form formed by the cell wall and the membrane so sort of like a dent so here we have the transvers septum and then after some time a transverse septum will be completely formed which will enable the daughter cells these two cells to separate now so now we have two bacteria cells and that completes binary fusion how the bacteria reproduces itself now the time taken for a cell the bacteria to reproduce itself is called the generation time and this can vary depending on the type of organism and the environment conditions so under favorable conditions for example the bacteria can reproduce um a lot under bad conditions they won't reproduce at all you can calculate the generation Time by doing simple simple mathematics so where generation time is equal to time taken divided by the number of Generations but we won't really look into that now what we will look into now however is the growth of a bacteria and we can um investigate the growth of bacteria by putting by isolating a bacteria and putting it inside a medium such as a Peter dish which makes the bacteria in culture now and under certain laboratory conditions we can view the growth phases of a bacteria bacteria has four growth phases and we can view this on a graph the x-axis of this graph is increase in time and the y- AIS is a logarithmic number of cells so this now we are looking at the four phases of growth for a bacteria the first phase is known as a lag phase and cells and in this phase the bacteria need to adapt to the new medium because it was just placed there after some time we have the log phase well cells are in Optimum growth State and perform binary fusion reprodu um re reproduction process and as you can see during the log phase there is a log logarithmic increase in cell number so what this means is that here we start off with one bacteria when it performs B Fusion we have two and then a binary fusion again we have two to the power of two we have four and then this process will continue 2 to ^ 3 and then 2 ^ 4 and this process where the bacteria keeps dividing in a linear sort of fashion is known as a logarithmic increase in growth or an exponential increase and so this is the log phase now after the log phase we have the third phase which is a stationary phase and this is and as you can see it just goes flat the number logarithmic number of cells just becomes flat it doesn't increase and this is due to the extion of some critical new nutrition or um the accumulation of waste product which basic essentially slows the growth or stops the growth of the bacteria in the culture and then after the stationary phase we have the death or decline phase and this is this essentially occurs through the continuation or accumulation of waste products or exposure to oxygen perhaps and in this phase you can see that the number of bacteria decreased I hope that made sense the graph I just drew essentially showed us the four phases of bacterial growth but of course the growth of the bacteria had to be under a good condition under laboratory conditions so essentially there are requirements for for bacterial growth and there are many factors which influence bacterial growth the fact the main factors affecting growth that we will look at now are temperature pH waste water sorry and osmotic pressure and also oxygen there's also nutritional requirements which we will not look into in this video before we continue on with the requirements for bacterial growth we have to understand that each bacteria is unique in that they require uh different uh different temperatures different pH different oxygen concentrations for growth and let's begin by looking at temperature first first and see how it affects bacterial growth by looking at a graph here we have a graph the Y AIS represents the rate of growth so the rate of bacteria grows and remember the growth of bacteria is not an increase in size but increase in number and the x-axis is the temperature from -10° cus to 80 degrees which is near boiling point right so this first graph where we see an increase in rate of growth um are are a group of bacteria known as cyrils and they are essentially cold blooded actually cold loving rather and their Optimum growth is about 10° C so really cold and we can see at the 10° cus that we have Optimum growth for these types of bacteria the other type of bacteria are known as mesophiles and their growth are Optimum at about between 25 to 35° C and as you can see by the graph the top is roughly around this area and then we have bacteria known as thermopiles which grow mostly um under hotter conditions where the optimum is about 60° C and after this we can even have o Other Extreme thermophiles which have Optimum growth over 80° C near nearly 100 so from this Gra of temperature we can see how there are different bacter different bacteria require different temperatures for Optimum growth next let's look at pH pH also is an important factor affecting bacterial growth pH if you know uh goes from0 to 14 where zero is um well towards zero is more acidic towards 14 is more basic different bacteria require different pH in order to grow optimally if they are grown in a in a in a pH that doesn't is not suitable for them they will die essentially bacterias which grow best in uh pH between Zer and six which is U more to the acidic side are known as acidophils meaning they love acids bacteria which grows optimally between a pH of six and N let's just say are called neutrophils because they're neutral and seven is a neutral pH then we have bacteria which grows Optimum under basic conditions so a pH of 10 and over they are known as alkalophilic the growth of a bacteria is the water and osmotic pressure bacteria grow best in areas saturated with water the increase in pressure of a back in a bacteria or a cell causes the cell to burst as well and so an Optimum pressure is required oxygen is is another fact factor which greatly influences bacterial growth because bacteria can be either anerobic or aerobic or in between so let's let's look at some classifications of of of um bacteria with oxygen first of all we have what's called obligate aerobes which means means these are the types of bacteria which requires oxygen in order to survive then we have facultative Anor robes which grow with or without oxygen but they grow better with oxygen then we have aerot tolerant Anor robes which are bacteries which grow equally well with or without oxygen obligate Anor robes are bacteria cells which die in the presence of oxygen and then we have these special special cases of bacteria such as micro ails which are Bia cells which won't grow at normal atmospheric oxygen levels which is 20% because so for example they won't grow in the room you are sitting in now but these bacteria require only some oxygen for growth between 2 and 10% then we have capil which are bacteria which require carbon dioxide they're carbon dioxide loving so from all these factors which affect bacterial growth I hope you can begin to appreciate um all these factors which can affect bacterial growth uh I hope this video was okay hope you enjoyed it made sense it might be confusion between generation time and growth phases you can read up on that if that's still confusing thank you

Channel: Armando Hasudungan

Views: 654,335

Keywords: microbiology, growth phases, lag, staitionary, decline death, logarithmic, exponential growth, bacteria, classification, reproduce, reproduction, optimum growth, temperature, ph, oxygen, anaerobes, aerobes, binary fussion, binary fission

Id: 7Lh-M-rX86Q

Length: 10min 41sec (641 seconds)

Published: Mon Feb 25 2013