Microbiology - Isolation of Bacteria from Soil

Isolation of bacteria from soil

Bacteria are the most numerous type of soil organism. Every gram of soil contains at least a million of these tiny one-celled organisms and highly fertile soils can have as much as 650 million bacteria per gram. There are many different species of bacteria, each with its own role in the soil environment. One of the major benefits bacteria provide for plants is in making nutrients available to them. Some species release nitrogen, sulfur, phosphorus, and trace elements from organic matter. Others break down soil minerals, releasing potassium, phosphorus, magnesium, calcium, and iron. Still other species make and release plant growth hormones, which stimulate root growth.

On the other hand, Multidrug-resistant organisms (MDROs) are a major concern for most hospitals. Causing infections for which antibiotic therapy is limited and in some cases no longer effective, they are associated with high morbidity and mortality rates and represent a significant burden on healthcare resources.

Three of the most common MDROs are :

• Methicillin-resistant Staphylococcus aureus (MRSA)
  According to CDC data, the proportion of Staphylococcus aureusinfections that are antimicrobial resistant has been growing significantly over the past few decades. In 1974, MRSA infections accounted for just two percent of the total number of S. aureusinfections; in 1995 this had risen to 22%; and by 2004, over 60% of infections showed resistance in the US.
   
• Extended spectrum ß-lactamase-producingEnterobacteria (ESBL)
  Microbial resistance through extended-spectrum ß-lactamase was first reported in the 1980s, soon after the introduction of 3rd generation cepahlosporins in clinical practice. Today, ESBL-producing Enterobacteria are recognized as nosocomial pathogens of major importance.
   
• Vancomycin-resistant enterococci (VRE)
  Enterococci with acquired vancomycin resistance are responsible for 1 in 3 infections in US intensive care units and VRE outbreaks more than doubled in Europe between 2001 and 2004.Transfer of vancomycin resistance from enterococci to staphylococci (VRSA) is a major threat for the healthcare community.

So, in this study soil of hospital grounds was chosen for isolation and characterization of bacteria.

MATERIALS

1.Soil samples hospital ground soil

2.Culture tubes

3. Petri plates

2.  Pipettes.

3. Molten (450C) and solid Muller hinton agar (MHA)

4. Balances and weighing boats.

6. Gram staining reagents

7.Sterile zip bags

8. Slides.

9. Electrical conductivity bridge

10. Ocular and stage micrometer

PROCEDURE

1. Soil sample containing hospital waste was collected from Bijoygarh, South Kolkata, West Bengal, India, in a sterile zip bag in the month of January.

1. 1g soil was dissolved in 10 ml sterile distilled water and was serially diluted upto 10-7   

[pic 1]

[pic 2]

1.  Plates were marked for each of the dilution.
2. 100µl of the inoculums was transferred to molten MHA (15ml) and was aseptically poured into each petri plate containing solified MHA and was mixed thoroughly.
3. The agar in the plates was allowed to solidify completely.
4. The plates were inverted and kept in the incubator at 37°C for 1 day.
5. Bacterial colonies in the Petri plates were selected after growth and were taken for colony characterization, Gram staining and measurement of cell.

RESULTS:

TABLE 1: Measurement of physical parameters of soil

TABLE 2: Colony characteristics of Samples: