<PAGE>

                                                                     Exhibit 4.2


                      1995 NONQUALIFIED STOCK OPTION PLAN
                    OF SOUTHERN RESEARCH TECHNOLOGIES, INC.

 Section 1.  Establishment, Purpose and Effective Date of Plan.
 -------------------------------------------------------------

     1.1  Establishment.  Southern Research Technologies, Inc., an Alabama
          -------------
corporation (the "Corporation"), hereby establishes a nonqualified stock option
plan for key Employees, Consultants and Directors of the Corporation which shall
be known as the "1995 NONQUALIFIED STOCK OPTION PLAN" (the "Plan").  Options
issued pursuant to the Plan will not be eligible for incentive treatment within
the meaning of Section 422 of the Internal Revenue Code of 1986, as amended (the
"Code").

     1.2  Purpose.  The purpose of the Plan is to advance the interests of the
          -------
Corporation, its subsidiaries and its shareholder (or shareholders) by
encouraging and providing for the acquisition of an equity interest in the
subsidiaries of the Corporation by key Employees, Consultants and Directors of
the Corporation through the grant of nonqualified stock options to key
Employees, Consultants and Directors.  The Plan is intended to enable the
Corporation to attract and retain the services of key Employees, Consultants and
Directors upon whose judgment, interest, and special effort the successful
conduct of its business operations is largely dependent.

     1.3  Effective Date. The Plan shall become effective on the date it is
          --------------
approved by the Board (the "Effective Date").

Section 2. Definitions.
----------------------

     2.1  Definitions
          -----------

          (a)  "Board" means the Board of Directors of the Corporation.

          (b)  "Consultant" means any person, whether an individual,
corporation, partnership, limited liability company or other entity, rendering
services to the Corporation as an independent contractor who is not paid by the
Corporation on a salaried or hourly basis.

          (c)  "Corporation" means Southern Research Technologies, Inc., an
Alabama corporation.

          (d)  "Director" means a member of the Board of Directors of the
Corporation.

          (e)  "Disability" means the permanent and total inability, by reason
of physical or mental infirmity, or both, of a Participant to perform the work
customarily assigned to him by the Corporation. The determination of the
existence or nonexistence of Disability shall be made by the Board pursuant to a
medical examination by a medical doctor selected or approved by the Board.
<PAGE>

     (f)  "Employee" means the Chairman of the Board, any Vice Chairman of the
Board, the President, Secretary or Treasurer of the Corporation, any Vice
President of the Corporation, any Assistant Secretary or Assistant Treasurer of
the Corporation, any other individual employed by the Corporation whom the Board
determines is a key employee.

     (g)  "Fair Market Value" means, on any given date (i) if shares of the
Subject Stock are not listed or admitted to trade on a national securities
exchange and if bid and asked prices for such Subject Stock are not furnished
through NASDAQ or a similar organization as described below, the value
established by the Board, in its sole discretion, for purposes of the Plan; (ii)
if such Subject Stock is listed or admitted to trade on a national securities
exchange or national market system, the closing price of the Subject Stock, as
published in The Wall Street Journal, so listed or admitted to trade on such
date or, if there is no trading of the Subject Stock on such date, then the
closing price of the Subject Stock on the next preceding date on which there was
trading in such shares; or (iii) if the Subject Stock is not listed or admitted
to trade on a national securities exchange or national market system, as
furnished by the National Association of Securities Dealers, Inc. through NASDAQ
or a similar organization if NASDAQ is no longer reporting such information.

     (h)  "Option" means the right to purchase Subject Stock at a stated price
for a specified period of time.

     (i)  "Participant" means an Employee, Consultant or Director designated by
the Board to participate in the Plan.

     (j)  "Retirement" (including "Early Retirement" and "Normal Retirement")
means termination of employment under the terms of the Corporation's then
current retirement program.

     (k)  "SBS" means Southern BioSystems, Inc., an Alabama corporation.

     (l)  "SRT-EO" means SRT Electro-Optics, Inc., an Alabama corporation.

     (m)  "Subject Stock" means 100,000 shares of the common stock of SRT-EO
owned by the Corporation and subject to issuance under this Plan, and 100,000
shares of the common stock of SBS owned by the Corporation and subject to
issuance under this Plan.

Section 3. Eligibility and Participation.  Participants in this Plan shall be
----------------------------------------
selected by the Board from among those Employees, Directors and Consultants who,
in the opinion of the Board, are in a position to contribute materially to the
Corporation's continued growth and development and to its long-term financial
success.  Participation shall be based on the recommendations of the
Corporation's Chief Executive Officer, subject to approval by the Board.
<PAGE>

Section 4. Administration.  The Board shall be responsible for the
-------------------------
administration of the Plan.  The Board, by majority action thereof, is
authorized to interpret the Plan, to prescribe, amend, and rescind rules and
regulations relating to the Plan, to provide for conditions and assurances
deemed necessary or advisable to protect the interests of the Corporation, and
to make all other determinations necessary or advisable for the administration
of the Plan, but only to the extent not contrary to the express provisions of
the Plan.  Determinations, interpretations, or other actions made or taken by
the Board pursuant to the provisions of the Plan shall be final and binding and
conclusive for all purposes and upon all persons whomsoever.

Section 5. Stock Subject to Plan.
--------------------------------

      5.1   Number.  The following number of shares of capital stock shall be
            ------
subject to issuance under this Plan: (a) 100,000 shares of the common stock, par
value $.01 per share, of SRT Electro-Optics, Inc., an Alabama corporation, owned
by the Corporation; and (b) 100,000 shares of the common stock, par value $.01
per share, of Southern BioSystems, Inc., an Alabama corporation, owned by the
Corporation.

       5.2  Unused Stock. In the event any shares of Subject Stock are subject
            ------------
to an Option which, for any reason, expires, terminates or, with the consent of
the Participant, is canceled as to such shares, such Subject Stock may again be
made subject to an Option pursuant to the Plan.

       5.3  Adjustment in Capitalization.  In the event of any change in the
            ----------------------------
outstanding shares of common stock of SRT-EO or SBS that occurs after the
Effective Date by reason of a stock dividend, stock split, recapitalization or
other similar corporate change in which the number of shares of the common stock
of either SRT-EO or SBS outstanding is increased, decreased or then changed,
then the aggregate number of shares of Subject Stock subject to each outstanding
Option, and its stated Option Price, and the aggregate number of shares of
Subject Stock shall be appropriately adjusted by the Board, whose determination
shall be conclusive; provided, however, that fractional shares shall be rounded
to the nearest whole share.

Section 6. Amendment, Modification, Termination and Duration of Plan.  The Board
--------------------------------------------------------------------
may at any time terminate, and from time to time may amend or modify, the Plan;
provided, however, that no amendment, modification, or termination of the Plan
--------  -------
shall in any manner adversely affect any Option theretofore granted under the
Plan, without the consent of the Participant.  The Plan shall remain in effect,
subject to the Board's right to earlier terminate the Plan, until all Subject
Stock shall have been purchased or acquired pursuant to the provisions hereof.
Notwithstanding the foregoing, no Option may be granted under the Plan on or
after the tenth (10/th/) anniversary of the Effective Date.
<PAGE>

Section 7. Terms of Options
---------------------------

     7.1    Grant of Options.  Subject to the provisions of Sections 3, 5 and 6
            ----------------
hereof, Options may be granted to Employees, Consultants and Directors at any
time and from time to time as shall be determined by the Board.

     7.2    Option Agreement. As determined by the Board on the date of grant,
            ----------------
each Option shall be evidenced by a written Option agreement that shall specify
the Option price, the duration of the Option, and the number of shares of
Subject Stock to which the Option pertains, together with other terms of the
Option.

     7.3    Option Price.  Options granted pursuant to the Plan shall have an
            ------------
exercise price that is equal to the Fair Market Value of the Subject Stock held
for issuance upon the exercise of such Option on the date such Option is
granted, or at such exercise price (whether greater or less than Fair Market
Value) determined by the Board.

     7.4    Duration and Vesting of Options. Each Option shall expire at such
            -------------------------------
time as the Board shall determine at the time it is granted, provided, however,
                                                             --------  -------
that no Option shall be exercisable later than the tenth (10/th/) anniversary
date of its grant. The Board shall also determine the period over which Options
shall vest or otherwise become exercisable, and shall have the authority under
this Plan to issue fully-vested Options.

     7.5    Exercise of Options. Options granted under the Plan shall be
            -------------------
exercisable at such times and be subject to such restrictions and conditions as
the Board shall in each instance approve, which need not be the same for all
Participants.

     7.6    Restrictions on Stock Transferability.  The Board shall impose such
            -------------------------------------
restrictions on any shares of Subject Stock acquired pursuant to the exercise of
an Option under the Plan as it may deem advisable, including, without
                                                              -------
limitation, the right of first refusal described below, restrictions under
----------
applicable federal securities law, under the requirements of any stock exchange
or automated quotation system upon which such shares of Subject Stock are then
listed or designated and under any blue sky or state securities laws applicable
to such shares.

     7.7    Right of First Refusal. If at any time during a Participant's
            ----------------------
lifetime, following the exercise of all or any portion of an Option granted
under this Plan, the Participant shall desire to sell all or any part of the
shares acquired by Participant pursuant to such Option (in this Section 7.7,
called the "Acquired Stock"), the Participant may sell the same only after
offering it to the Corporation in the following manner:

            (a)  The Participant shall serve notice upon the Corporation stating
that the Participant has received a bona fide offer for the sale of shares of
the Acquired Stock and setting forth the following information: (i) the number
of shares of the Participant's Acquired Stock proposed to be sold; (ii) the name
and address of the person offering to purchase such Acquired Stock; and (iii)
the sale price and terms of payment of such sale. Such notice shall also contain
an offer by the Participant to sell such shares of the Acquired Stock to the
Corporation at the price offered by such bona fide offeror.
<PAGE>

               (b)  For a period of thirty (30) days after receipt of such
notice, the Corporation shall have the right to purchase all or a portion of the
shares of Acquired Stock so offered. If the Corporation fails to exercise such
right with respect to all or a portion of such shares of Acquired Stock, the
Participant shall be free to sell such remaining shares of Acquired Stock to the
person named in the aforesaid notice at a price and upon the terms and
conditions set forth in such notice; provided, however, that such disposition
                                     --------  -------
shall be made within thirty (30) days following the termination of the right of
the Corporation to purchase such shares of Acquired Stock.

               (c)  The terms of this Subsection 7.7 shall terminate as to
Acquired Stock of a subsidiary of the Corporation upon the successful
consummation by such subsidiary of an initial public offering of securities of
the class including the Acquired Stock registered under the Securities Act of
1933, as amended, from which such subsidiary receives cash proceeds in excess of
$15,000,000.

          7.8  Payment.  The exercise price due upon the exercise of any Option
               -------
shall be payable to the Corporation in full in cash or its equivalent; provided,
however, that the Participant may elect to instruct the Corporation to, in lieu
of requiring cash payment from Participants to exercise Options issued under the
Plan, issue a number of shares of Subject Stock equal to the product of (a) the
number of shares of Subject Stock purchasable under the Option, or portion
thereof being exercised, and (b) the Fair Market Value of one share of Subject
Stock minus the exercise price attributed to such share, divided by (c) the Fair
Market Value of one share of Subject Stock. The proceeds from any payment shall
be added to the general funds of the Corporation and shall be used for general
corporate purposes.

          7.9  Termination of Employment Due to Death, Disability, or
               ------------------------------------------------------
Retirement. In the event the employment of a Participant is terminated by reason
----------
of death, Disability or Retirement, the rights under any then outstanding Option
granted pursuant to the Plan shall terminate upon the expiration date of the
Option or ninety (90) days after such date of termination of employment,
whichever first occurs.

          7.10 Termination of Employment Other Than for Death, Disability, or
               --------------------------------------------------------------
Retirement.  If the employment of the Participant shall terminate for any reason
----------
other than death, Disability, or Retirement, the rights under any then
outstanding Option granted pursuant to the Plan shall terminate upon the
expiration date of the Option or thirty (30) days after such date of termination
of employment, whichever first occurs.

          7.11 Non-transferability of Options. No Option granted under the Plan
               ------------------------------
may be sold, transferred, pledged, or assigned, or otherwise alienated or
hypothecated, except by will or by the laws of descent and distribution.
Further, during the Participant's lifetime, Options granted to such Participant
under the Plan are exercisable solely by such Participant.

Section 8. Rights of Employees.  Nothing in the Plan shall interfere with or
------------------------------
limit in any way the right of the Corporation to terminate any person's
employment or other relationship with the Corporation at any time, nor confer
upon any person any right to continue in the employ of the Corporation.
<PAGE>

Section 9. Dissolution; Merger.  Upon the dissolution or liquidation of the
------------------------------
Corporation, SRT-EO or SBS, or upon a reorganization, merger or consolidation of
the Corporation, SRT-EO or SBS as a result of which the outstanding securities
of the class then subject to Options hereunder are changed into or exchanged for
cash or property or securities not of the issue of the Corporation, SRT-EO or
SBS, as applicable, or any combination thereof, or upon a sale of substantially
all the assets of the Corporation, SRT-EO or SBS to another person, corporation,
partnership, limited liability company or other entity, then if the Corporation
is the direct subject of such an event this Plan shall terminate, and all
Options theretofore granted hereunder shall terminate, unless provision be made
in writing in connection with such transaction for the continuance of the Plan
and/or for the assumption of Options theretofore granted, or the substitution
for such Options of options covering the stock of a successor corporation or
entity, or a parent or a subsidiary thereof, with appropriate adjustments as to
the number and kind of shares and prices, in which event the Plan and Options
theretofore granted shall continue in the manner and under the terms so
provided; provided, however, that if either SRT-EO or SBS is the direct subject
          --------  -------
of such a transaction, then this Plan shall terminate only as to Options for the
common stock of either SRT-EO or SBS, as applicable, unless provision be made in
writing in connection with such transaction for the continuance of the Plan with
respect to such Options and/or for the assumption of such Options, or the
substitution for such Options of options covering the stock of a successor
corporation or entity, or a parent or a subsidiary thereof, with appropriate
adjustments as to the number and kind of shares and prices, in which event this
Plan and such Options theretofore granted shall continue in the manner and under
the terms so provided.  If the Plan (or its applicability to any Subject Shares
of SRT-EO or SBS) and unexercised Options shall terminate pursuant to the
foregoing sentence, all persons entitled to exercise any unexercised portions of
Options then outstanding shall have the right, at such time prior to the
consummation of the transaction causing such termination as the Corporation
shall designate, to exercise the unexercised portions of their Options,
including the portions thereof which would, but for this Section 9, not yet be
exercisable.

Section 10. Tax Withholding.  Whenever shares of Subject Stock are to be issued
---------------------------
under the Plan, the Corporation shall have the power to require the recipient of
the Subject Stock to remit to the Corporation an amount sufficient to satisfy
federal, state, and local withholding tax requirements.  The Corporation also
shall have the power to withhold an appropriate number of shares of Subject
Stock sufficient to satisfy federal, state and local withholding tax
requirements upon the exercise of an Option under the Plan.

Section 11. Indemnification.  Each person who is or shall have been a member of
---------------------------
the Board shall be indemnified and held harmless by the Corporation against and
from any loss, cost, liability, or expense that may be imposed upon or
reasonably incurred by him in connection with or resulting from any claim,
action, suit, or proceeding to which he may be a party or in which he may be
involved by reason of any action taken or failure to act under the Plan and
against and from any and all amounts paid by him in settlement thereof, with the
Corporation's approval, or paid by him in satisfaction of any judgment in any
such action, suit, or proceeding against him, provided he shall give the
Corporation an opportunity, at its own expense, to handle and defend the same
before he undertakes to handle and defend it on his own behalf.  The foregoing
right of indemnification shall not be exclusive of any other rights of
indemnification to which such persons may be entitled under the Corporation's
Articles of Incorporation or Bylaws, as a matter of law, or otherwise, or any
power that the Corporation may have to indemnify them or hold them harmless.
<PAGE>

Section 12. Requirements of Law; Miscellaneous.
----------------------------------------------

     12.1  Requirements of Law.  The granting of Options for Subject Stock, the
           -------------------
issuance of shares of Subject Stock upon the exercise of an Option , and the
sale or transfer of such issued Subject Stock shall be subject to all applicable
laws, rules, and regulations, and to such approvals by any governmental agencies
or national securities exchanges as may be required.

     12.2  Governing Law.  The Plan, and all agreements hereunder, shall be
           -------------
construed in accordance with and governed by the substantive laws of the State
of Alabama, without regard or reference to the choice of law provisions or laws
of such State.

     12.3  Gender and Number.  Except when otherwise indicated by the context,
           -----------------
words in the masculine gender when used in the Plan shall include the feminine
gender, the singular shall include the plural, and the plural shall include the
singular.

     12.4  Expenses. The Corporation shall bear the expenses of administering
           --------
the Plan.

                                  * * * *
<PAGE>

                             AMENDMENT NUMBER ONE
                                    TO THE
                     SOUTHERN RESEARCH TECHNOLOGIES, INC.
                      1995 NONQUALIFIED STOCK OPTION PLAN

     The following amendment shall be effective as of January 1, 1997:

1.   Amend Section 7.9 Termination of Employment Due to Death, Disability, or
                       ------------------------------------------------------
Retirement by deleting the section and substituting in lieu thereof the
----------
following:

     7.9  Termination of Employment or Termination of Service as a Consultant or
          ----------------------------------------------------------------------
     Director Due to Death, Disability, or Retirement.
     ------------------------------------------------

     In the event a Participant terminates employment with the Corporation or
     service as a Consultant or Director to the Corporation by reason of death,
     Disability or Retirement, the rights under any then outstanding Option
     granted pursuant to the Plan shall terminate upon the expiration date of
     the Option or ninety (90) days after such date of termination of service or
     employment, whichever first occurs.

2.   Amend Section 7.10 Termination of Employment Other Than for Death,
                        ----------------------------------------------
Disability, or Retirement by deleting the section and substituting in lieu
-------------------------
thereof the following:

     7.10  Termination of Employment or Termination of Service Other Than for
           ------------------------------------------------------------------
     Death, Disability, or Retirement.  If a Participant terminates employment
     --------------------------------
     or service as a Consultant or Director for any reason other than death,
     Disability, or Retirement, the rights under any then outstanding Option
     granted pursuant to the Plan shall terminate upon the expiration date of
     the Option or thirty (30) days after the date of termination of such
     employment or service, whichever first occurs; provided, however, in the
     event the Employee terminates employment with the Corporation or a
     Consultant or Director terminates service with the Corporation for any
     reason other than death, Disability, or Retirement but continues or within
     thirty (30), days thereafter begins service as a Consultant or Director or
     employment as an employee of an affiliate of the Corporation or a company
     in which the Corporation holds a significant ownership interest, any
     outstanding Option granted pursuant to the Plan shall continue until the
     earlier of (A) the expiration date of the Option or (B) thirty (30) days
     after termination of such service or employment unless termination is by
     reason of death, Disability or Retirement in which case ninety (90) days
     shall be applicable.  For purposes of this section, "significant ownership
     interest" shall mean any direct or indirect ownership interest of twenty-
     five percent (25%) or more of the total combined voting power of all
     classes of stock entitled to vote or twenty-five percent (25%) or more of
     the total value of the shares of all classes of stock of the company.

3.   All other provisions of the Plan shall remain in full force and effect.
<PAGE>

     IN WITNESS WHEREOF, Southern Research Technologies, Inc. has caused this
Amendment Number One to be executed by its authorized officers this _____ day of
____________, 1997.

ATTEST:                      SOUTHERN RESEARCH TECHNOLOGIES, INC.


_________________            By:_____________________________
Secretary
                             Its:____________________________
<PAGE>

                             AMENDMENT NUMBER TWO
                                    TO THE
                     SOUTHERN RESEARCH TECHNOLOGIES, INC.
                      1995 NONQUALIFIED STOCK OPTION PLAN

       The following amendment shall be effective as of January 1, 1997:

1.     Amend Section 7.9 Termination of Employment of Service
                         ------------------------------------
as a Consultant or Director Due to Death, Disability, or Retirement by deleting
-------------------------------------------------------------------
the section and substituting in lieu thereof the following:

       7.9    Termination of Employment or Termination of Service as
              ------------------------------------------------------
a Consultant or Director Due to Death, Disability, or Retirement.
----------------------------------------------------------------

       In the event a Participant terminates employment with the Corporation or
service as a Consultant or Director to the Corporation by reason of death,
Disability or Retirement, the rights under any then outstanding Option granted
pursuant to the Plan shall terminate upon the expiration date of the Option or
ninety (90) days after such date of termination of service or employment,
whichever first occurs, unless the Board shall have authorized an extension of
the Option to a period not to exceed the expiration date of the Option.

2.     Amend Section 7.10 Termination of Employment of Service
                          ------------------------------------
as a Consultant or Director Due to Death, Disability or Retirement by deleting
------------------------------------------------------------------
the section and substituting in lieu thereof the following:

       7.10   Termination of Employment or Termination of Service
              ---------------------------------------------------
Other Than for Death, Disability, or Retirement.  If a Participant terminates
-----------------------------------------------
employment or service as a Consultant or Director for any reason other than
death, Disability, or Retirement, the rights under any then outstanding Option
granted pursuant to the Plan shall terminate upon the expiration date of the
Option or thirty (30) days after the date of termination of such employment or
service, whichever first occurs, unless the Board shall have authorized an
extension of the Option to a period not to exceed the expiration date of the
Option; provided, however, in the event the Employee terminates employment with
the Corporation or a Consultant or Director terminates service with the
Corporation for any reason other than death, Disability, or Retirement but
continues or within thirty (30) days thereafter begins service as a Consultant
or Director or employment as an employee of an affiliate of the Corporation or a
company in which the Corporation holds a significant ownership interest, any
outstanding Option granted pursuant to the Plan shall continue until the earlier
of (A) the expiration date of the Option or (B) thirty (30) days after
termination of such service or employment unless termination is by reason of
death, Disability or Retirement in which case ninety (90) days shall be
applicable, unless the Board shall have authorized an extension of the Option to
a period not to exceed the expiration date of the Option.  For purposes of this
section, "significant ownership interest" shall mean any direct or indirect
ownership interest of twenty-five percent (25%) or more of the total combined
voting power of all classes of stock entitled to vote or twenty-five percent
(25%) or more of the total value of the shares of all classes of stock of the
company.

3.     All other provisions of the Plan shall remain in full force and effect.
<PAGE>

     IN WITNESS WHEREOF, Southern Research Technologies, Inc. has caused this
Amendment Number Two to be executed by its authorized officers this _____ day of
____________, 1997.

ATTEST:                      SOUTHERN RESEARCH TECHNOLOGIES, INC.


____________________         By:_______________________________
Secretary
                             Its:______________________________
<PAGE>

                             AMENDMENT NUMBER TWO
                                    to the
                    1995 NONQUALIFIED STOCK OPTION PLAN OF
                     SOUTHERN RESEARCH TECHNOLOGIES, INC.



          THIS INSTRUMENT, made and entered into this 19 day of May, 1998, by
SOUTHERN BIOSYSTEMS, INC., an Alabama corporation (the "Company").


                                 R E C I T A L S
                                 - - - - - - - -


          A.  Effective as of May 19, 1998, Southern BioSystems, Inc., ("Old
SBS") was merged with and into the Company, which was at that time known as
Southern Research Technologies, Inc. (the "Merger").  Simultaneously with the
Merger, the Company changed its name to Southern BioSystems, Inc.


          B.  Prior to the Merger, the Company maintained a stock option plan,
known as the 1995 Nonqualified Stock Option Plan of Southern Research
Technologies, Inc., as amended by Amendment Number One dated January 1, 1997
(the "SRT Plan").  The SRT Plan provided for grants of options by the Company to
certain of its employees, directors, and consultants to acquire shares of common
stock in SRT Electro-Optics, Inc. ("SRT EO") and Old SBS owned by the Company.
SRT EO was liquidated, and all options issued under the SRT Plan to acquire
stock in SRT EO were cashed out.  In connection with the Merger, the shares of
common stock of Old SBS owned by the Company were canceled.  The Company desires
to continue the SRT Plan and to substitute one share of common stock of the
Company for each share of common stock of Old SBS subject to options outstanding
under the SRT Plan at the effective time of the Merger and to substitute one
share of common stock of the Company for each share of common stock of Old SBS
with respect to which options had not been granted at the time of the Merger but
which, but for the cancellation of the Old SBS common stock, would have been
available for grants of options under the SRT Plan.  Under the terms of the
Separation Agreement providing for the Merger, options granted under the SRT
Plan to the individuals listed in Exhibit I to acquire shares of common stock of
Old SBS were canceled as of the effective time of the Merger.


          NOW, THEREFORE, pursuant to Section 6 of the SRT Plan and the terms of
the Separation Agreement providing for the Merger, the Company does hereby amend
the SRT Plan as follows:

          1.  All references in the SRT Plan to the "Corporation" shall, from
and after May 19, 1998, be deemed references to the Company.
<PAGE>

          2.  All references in the SRT Plan to "Stock" shall be deemed to be
references to the common stock of the Company, each share of which shall be
deemed to be equal to one share of common stock of Old SBS.


          3.  The options granted prior to May 19, 1998, under the SRT Plan to
acquire shares of common stock of Old SBS, other than those granted to the
individuals named in the Exhibit I, shall be exercisable in accordance with
their terms for shares of common stock of the Company on the same basis as if
such shares were shares of common stock of Old SBS.


          4.  Options granted under the SRT Plan prior to May 19, 1998, to the
individuals listed in Exhibit I were canceled in accordance with the terms of
the Separation Agreement providing for the Merger and shall not be exercisable
after the effective date of the Merger.


          5.  Options granted under the SRT Plan to acquire shares of common
stock of SRT EO were cashed out and no such option shall be exercisable after
the date hereof.  No option to acquire shares of common stock of SRT EO shall be
granted under the SRT Plan after said date.


          IN WITNESS WHEREOF, the Company has caused this instrument to be
executed by its officer thereunto duly authorized on this 19 day of May, 1998.


                                    SOUTHERN BIOSYSTEMS, INC.


                              By:    /s/ W. B. Smith
                                  -----------------------------------

                              Its:   President
                                   ----------------------------------

                                      13

<PAGE>

                                   Exhibit I
                                   ---------

Herbert Blatter

                                     -14-